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An improved automated bloodstain pattern analysis method has been developed and validated, which utilises computer vision techniques to identify bloodstains on a plain background within a digital image. The method generates metrics relating to the individual stains as well as the overall pattern, including bloodstain pattern specific metrics such as the gamma angle, circularity, solidity, area of convergence, stain density and pattern linearity. This method provides an objective approach to the analysis of bloodstains and bloodstain patterns and can generate a wealth of quantitative data that is currently not obtainable using manual techniques or other image-based programs currently utilised in the discipline. This method will be useful to analysts and researchers investigating the application of quantitative methods to bloodstain pattern analysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Bloodstain pattern analysis (BPA) on absorbent surfaces, such as fabrics, is far more complex compared to its application on smooth, hard, non-porous surfaces. Angle of impact and directionality are commonly interpreted from bloodstains but may be adversely affected by porous surfaces. In fact, there is a lack of evidence that traditional approaches to BPA are even applicable when blood impacts absorbent materials such as clothing and other fabrics. Hence, there is a critical need for research focusing on the validity and reliability of methods for bloodstain pattern analysis on textiles. Here, human blood drops were deposited on six different fabric types (cotton, satin polyester, rayon, blended polyester/spandex, blended nylon/spandex, and blended modal/polyester/spandex) at two known impact angles: 30° and 10°. Bloodstain morphology was found to be unique for each fabric. Calculated angles of impact for cotton and satin polyester were not statistically different from the known angle of impact while blended polyester/spandex, blended nylon/spandex, and blended modal/polyester/spandex significantly underestimated the known angle of impact. Even when stain morphology on fabric resembled those on a glass control, the angle of impact significantly underestimated the known. The ability to assign directionality based upon bloodstain morphology was dependent on the fabric type. These findings support the need for further research and the development of guidelines for bloodstain pattern interpretation on fabric materials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper, (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Bloodstain pattern analysis plays a crucial role in forensic investigations. Projected patterns can offer valuable insights into the dynamics of crime scenes. In this paper, we propose and validate a novel approach that extends existing software, HemoVision, to analyze impact patterns that are distributed across multiple arbitrarily oriented surfaces. The proposed method integrates HemoVision's marker-based system with structure from motion (SfM) techniques to reconstruct the three-dimensional geometry of impact patterns using only two-dimensional photographs. Controlled experiments were used to validate the proposed approach, demonstrating robustness in reconstruction accuracy with median translation errors below 3 mm and median angular errors below 0.2°, irrespective of imaging device or image resolution. Comparing the estimated areas origin to their known ground truth, the proposed method achieved an average total error of 8.12 cm, with the primary source of error being the vertical dimension. Despite this, the overall error remains well within the ranges of error reported in prior work. This study demonstrates that HemoVision can be used to analyze complex impact patterns using only two-dimensional photographs, providing forensic experts with an efficient and accessible tool for investigating intricate crime scenes involving multi-surface impact patterns., Competing Interests: Declaration of Competing Interest Philip Joris and Ruben Moermans are employed by Forentrics, the organization responsible for the development and marketing of the product (HemoVision) described in this paper. Els Jenar, Dirk Vandermeulen, and Peter Claes are not employed by Forentrics, but hold shares of said company. As employees and shareholders of Forentrics, the authors may have a financial interest in the success of the product. However, this potential conflict of interest did not influence the design, execution, or interpretation of the research presented in this manuscript. The findings and conclusions presented herein are based solely on scientific merit and unbiased analysis., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Classifying bloodstains is an essential part of Bloodstain Pattern Analysis. Various experts have developed methods. Each method considers the same basic bloodstain pattern types. These use either terminology based on the observable characteristics or the mechanistic cause of the bloodstain patterns as part of the classification process. This review paper considers ten classification methods from fourteen sources, which are used to classify bloodstain patterns. There are fundamental differences in how the patterns are classified, how differentiated the classification is, and whether the classification process uses clear, unambiguous criteria, and is susceptible to contextual bias. Experts have also reported issues with classifying bloodstains that have indistinguishable features. These differences expose key limitations with current classification methods: mechanistic terminology is too heavily relied on, and the classification process is susceptible to contextual bias. The development of an unambiguous classification method, based on directly observable characteristics within bloodstain patterns is recommended for future work., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

In bloodstain pattern analysis (BPA), a field of forensic science, there has been active discussion on the estimation of the area of origin of impact spatter. However, there is no established methodology to quantitatively analyze the area of origin of a swing cast-off pattern. To quantitatively analyze the methodology of previous research on estimation of area of origin, a device for generating uniform swing cast-off patterns was produced. Using artificial blood, 10 swing cast-off patterns were generated on porous paper; in each, 10 blood drops were selected for the calculation of the impact angle. Hemospat software was used for individual bloodstain analysis, and an open source code was used for estimation of area of origin. Under the same conditions, an additional 10 swing cast-off patterns were generated, and quantitative analysis was performed using trigonometric functions and an adjustment formula that minimized errors in calculating the impact angle. The adjustment formula was corrected to calculate the impact angle for the bloodstains on the porous surface. As uncertainty decreases, the error increases, and the point at which both uncertainty and error can be minimized is calculated as 75%. The existing formula included the trajectory in the estimated likelihood range in 75% of samples. When the adjustment formula was applied, the accuracy was improved, with the trajectory included in the area with a 90% likelihood., (© 2024 The Authors. Journal of Forensic Sciences published by Wiley Periodicals LLC on behalf of American Academy of Forensic Sciences.)

There are numerous crime scene investigation applications of 3D scanning that have been previously documented. This paper documents the application of a 3D point cloud in the presentation of Bloodstain Pattern Analysis evidence to mock jurors. 150 mock jurors viewed a presentation of Bloodstain Pattern Analysis evidence from a murder trial in the UK. After viewing the evidence, the participants were tested on their knowledge of the evidence and repeated the test again 2 weeks later; to simulate criminal trial conditions; whereby there is a time lapse between the initial viewing of evidential material and deliberation. This paper found that the mock jurors who additionally viewed a 3D flythrough of a point cloud of the crime scene, better retained knowledge of the evidence over time, reported a greater ability to visualise the crime scene and had higher levels of interest in the evidence. Crucially, the 3D flythrough group did not report different levels of confidence in the accuracy of their memories of the evidence, nor different levels of emotional arousal to the group that viewed the evidence without the 3D presentation. Together, these findings suggest that 3D scanning of crime scenes, and the resultant point cloud's presentation to jurors, could add further value to the justice system when spatial information, such as Bloodstain Pattern Analysis evidence, is presented., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Bloodstain pattern analysis (BPA) has proven to be a useful tool in forensic and criminal investigations for quite some time. Traditionally, documenting a crime scene for a bloodletting event was completed using manual techniques, physical strings, and a tape measure. In more recent years, laser scanners and 3D software programs have become a preferred method to capture accurate data that improves the validity and reliability of BPA. The initial cost of laser scanning equipment is relatively high, rendering these systems inaccessible to some police and smaller agencies. Recon-3D is a newly developed iPhone application that utilizes the iPhone LiDAR sensor in combination with video data to create 3D point clouds of crime scenes. To assess the viability of Recon-3D for area of origin analysis, two tests were performed. One was a series of bloodstain impacts which were analyzed in FARO Zone 3D software, while the second was a series of 6 repeated Recon-3D scans of two 90-degree walls which was then compared to the FARO Focus S350 scanner using CloudCompare software. A total of eight impact patterns were made at three different distances from a wall. The area of origin was measured and compared to the known location of the blood source. The average total 3D error for the area of origin set at 25, 50, and 100 cm from two perpendicular walls was found to be 6.04, 15.16, and 36.59 cm, respectively. These results are similar to past studies where programs such as HemoSpat have been used. The results of the point cloud comparison show that on average, 95% of the points from Recon-3D fall below a threshold of 3.6 mm when compared to a FARO Focus S350 laser scanner. Thus, the results of this test suggest that Recon-3D is an accurate and affordable scanning application for bloodstain patterns at crime scenes and the data provide acceptable results for area of origin analysis in BPA programs which accept laser scanner data., (© 2024 The Authors. Journal of Forensic Sciences published by Wiley Periodicals LLC on behalf of American Academy of Forensic Sciences.)

The first point of contact between a spherical blood drop and a surface is related to the angle between the trajectory of the blood drop and the surface being struck. This angle is often referred to as the impact angle which can be estimated by knowing the width and length of the resultant elliptical bloodstain. Most software programs dedicated to area of origin analysis indicate the location of the backtracked bloodstain trajectory to be at the geometric centre or at the tip of the bloodstain ellipse. However, it is unknown how the first point of contact and the blood drop trajectory (here defined as the locus of the centre of mass of the drop as it travels) are related empirically. Thus, this study aims to look at how the initial point of contact and the trajectory at the impact of a blood drop relates to the formed bloodstain ellipse. Two volumes of blood (0.013 ml and 0.071 ml) were dropped from a height of 10 cm and 40 cm onto an inclined surface at 0°, 15°, 30°, 45°, 60°, and 75°. The transition from a spherical blood drop to an elliptically shaped bloodstain was recorded using a high-speed camera for all tests. A total of 72 ellipses were analyzed to determine the location of the first point of contact and trajectory point of the blood drop and how they relate to the formed elliptical bloodstain. A relationship was found between the first point of contact and the bloodstain trajectory which was dependent on the impact angle. However, there were clear deviations from theoretical assumptions due to blood drop oscillations, the effects of gravity, and the natural fluid characteristics of blood. The results of this study may assist bloodstain pattern analysts and software developers by more accurately applying the location of the blood drop trajectory based on empirical data., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Bloodstains are typically encountered in violent incidents involving the use of a weapon or physical actions, such as punching, kicking, or stamping. Bloodstain pattern analysis can provide inceptive evidence or intelligence about what happened in an alleged incident, the sequence of events, along with indicating possible suspects if blood is analysed through DNA profiling. This research project focused on the differences in patterns created on footwear during a violent action, such as stamping on a person, and a non-violent action, such as walking through a pool of blood. In this project, several experiments were designed to simulate the stamping and walking actions on a surface wet with blood: carpet, lino flooring, and belly pork meat. Two volunteers with varying body weights were recruited to perform the two actions, using a pair of trainers and a pair of Wellington boots. Defibrinated horse blood was used to simulate real human blood. It was found that the patterns created from stamping and walking through blood differed by the type of pattern and the number and size of stains. The footwear used in the stamping action was characterised by a larger contact stain on the sole than those used in the walking actions: ∼209 mm in length by ∼92 mm in width versus ∼65 mm in length by ∼60 mm in width. The stamping action produced a large number of impact spatters (∼435) on the sides of the footwear versus no impact spatters in the walking actions. The presence of impact spatters was found to be the most prominent feature that differentiated between the two actions. The findings were statistically significant (p < 0.05) and could assist in evaluating whether a defendant was actively involved in a stamping action, or the evidence found was due to innocent reasons., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

The impact of whole human blood drops on jeans fabrics is studied as a function of the impact velocity U 0 , room relative humidity RH, and spacing S between the fabric and backing substrate. Experiments are performed with blood drops of the same initial diameter of D 0 = 3 ± 0.08 mm and temperature of 37 ∘ C. Whole human blood is collected from the same donor. The impact dynamics of blood drops is described as a function of U 0 and S, and it is shown that the spacing has an effect on the splashing limit and the surface area of the drip stains. At RH = 30%, the drip stains (parent stains) after impact do not wick the fabrics. Moreover, the area of the drip stains increases with the impact velocity until a critical value (U 0 = 3.3 ± 0.1 m∕s), where it becomes constant. A modified correlation is proposed to predict the drip stains area. At RH = 70%, the drip stains after impact wick the jeans fabrics. The area of the drip stains after impact is dependent on the impact velocity while the final area after wicking is not. Further, the contribution of the wicking, to the formation of the drip stains, decreases with the impact velocity. These findings show the importance of taking into account RH in future research work and in the analysis of the drip stains at crime scenes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The findings from a bloodstain pattern analysis (BPA) may assist in formulating or falsifying scenarios that are considered in the investigative stages of a criminal investigation. When a case proceeds to trial the bloodstain pattern expert may be asked about the relevance of their findings given scenarios that are proposed by the prosecution and defense counsel. Such opinions provided by an expert are highly relevant to police investigation or legal proceedings, but the reasoning behind the opinion or implicit assumptions made by the expert may not be transparent. A proper framework for the evaluation of forensic findings has been developed since the late twentieth century, based on the hierarchy of propositions, Bayesian reasoning and a model for case assessment and interpretation. This framework, when implemented in casework, mitigates some of the risks of cognitive biases, and makes the reasoning and scientific basis for the opinion transparent. This framework is broadly used across forensic science disciplines. In this paper we describe its application to the field of BPA using a case example from the Netherlands Forensic Institute (NFI)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.)

Understanding the underlying hydrodynamics of impinging blood droplets and finding out the physical parameters determining the bloodstain characteristics are of great importance in blood related forensic investigations. In this work, the impact of non-Newtonian blood droplets on solid surfaces ranging from lyophilic to superlyophobic was systematically investigated and compared to that of Newtonian droplets with a similar dynamic shear viscosity. We show that impinging blood droplets behave as low-viscosity Newtonian droplets in the short-time spreading, which is dominated by capillary and inertial forces, but their non-Newtonian viscoelasticity would notably affect the droplet retraction and post-impact oscillation occurring in large timescales. Whereas the strong liquid-solid adhesion and the non-Newtonian elongational viscosity hinder droplet recoiling and thus alter the impact phenomena on lyophobic and superlyophobic surfaces, the shear and elongational viscosities are coupled to result in higher damping coefficients of oscillating blood droplets after deposition, in comparison to that of impinging Newtonian droplets. The size of the dried bloodstain was found to be different from both the maximum spreading radius of the droplet that can reach during impact and the final radius of the deposited droplet after oscillation, and their correlations are highly dependent on the impact velocity and surface wettability. Moreover, the morphologic characteristics of the bloodstains would also be changed by varying either the impact velocity or the surface wettability. We envision that these findings can not only find applications in the bloodstain pattern analysis, but also provide useful information for medical diagnosis based on blood droplet test., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.)

Given the use of modified blood products (e.g. leucocyte depleted erythrocyte concentrates in SAG-mannitol, dehydrated blood powder, defibrinated blood), drawing blood from conscious animals while minimizing their stress is a good option to obtain blood for bloodstain pattern analysis. Nevertheless, the blood must be well described since individual differences in quality can occur, and storage will influence blood components qualitatively and quantitatively. Cow has been discussed as a suitable source of blood supply, but current data lack hematological and full rheological perspectives. This project includes the respective parameters in combination with passive drip pattern experiments during refrigerated storage in multiple study arms. Cow blood displayed a constant increase in viscosity (at high shear rate: 1000s -1 ), reflecting the expected reduction in red blood cell (RBC) flexibility. RBCs shrank but remained intact with very few irregular shapes, therefore there was no evidence of hemolysis. Influence of storage on stain size in passive drip pattern experiments with different substrates was minimal. However in cows, it is not hemolysis but an early change in suspension properties that indicates storage lesion. Viscosity (at low shear rate: 1s -1 ) of some blood samples increased three-fold (peaking at day 14), transitioning sharply to near-Newtonian (almost shear-independent) behavior thereafter. The higher this increase in viscosity, the greater the increase in the number of satellite spatter on glass. In order to ensure high quality simulations in the future, comprehensive rheological analyses to detect gradual changes in blood pseudoplasticity should be implemented in the forensic discipline of bloodstain pattern analysis., Competing Interests: The authors declare no conflict of interest, (© 2023 The Authors.)

Research informed by practice is more likely to have a greater impact on society. However, forensic cases are confidential and thus, real-life data regarding the details of violent crime is usually withheld from the public and academia. Through a partnership between the authors institution and a UK police service, casefiles from 78 criminal investigations from 2012 to 2020 involving Bloodstain Pattern Analysis (BPA) were examined and quantified. The most common methods of assault and weapons used were identified as well as the frequency of different bloodstain pattern classifications. The results of this study will help inform researchers and supply forensic training providers with data derived from forensic practice. Despite a significant body of literature exploring impact patterns and software for calculating the Area of Origin (AO), impact pattern was classified at only 22% of scenes, with sharp-force trauma being the most prevalent form of assault. This paper recommends a review of the BPA terminology, to include additional commonly encountered patterns that are not defined by the current standard., Competing Interests: Declarations of Interest The authors declare that they have no conflict of interest., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Two men were wrongfully convicted of murder in 2017 and sentenced to life imprisonment. After a physical altercation inside a flat, the victim (A) was found dead approximately 60 m away outside a residential address. He had sustained a number of injuries including a stab wound to the left side of his neck which was found to have divided the right carotid artery. The location where A was found was not regarded as a crime scene and not subjected to a specialist forensic examination by scientists as it was assumed that the fatal injury was sustained in the flat. The pathologist, who subsequently carried out the autopsy on A, was not asked to attend the scene. A review of the blood distribution at the scene in conjunction with the pathology findings indicated however that the fatal neck wound had been inflicted outside the flat, near to where the victim was found. An appeal against the convictions for murder was upheld in 2021 and a re-trial ordered. Following this second trial, both accused were acquitted of murder and released from custody. The new pathology and blood pattern evidence introduced at the second trial was a major part of the defense strategy which led to the acquittal of the accused. The case illustrates that a more inclusive and detailed crime scene strategy had been undertaken, including an assessment of the bloodstains present, in conjunction with discussion with the pathologist, then the likelihood is that the two men subsequently charged with murder would have been eliminated as suspects and a miscarriage of justice would have been avoided., (© 2022. The Author(s).)

In the investigation of gunshot deaths, Bloodstains Pattern Analysis (BPA) and, in particular, backspatter patterns found on the body of the suspect/victim and on the surfaces close to the entrance wound of the bullet can provide investigators with important indications on the dynamics of the events. Backspatter patterns have, however, morphological characteristics common to other bloodstains of different origin, so, in order to positively identify them, a possible solution is represented by their sampling, using an aluminum stub for electron microscopy, for the detection of gunshot residues (GSR) present. The latter, however, if present below the small blood crusts, could be difficult to detect during analysis by Scanning Electron Microscopy/Energy Dispersive X-ray microanalysis (SEM/EDX). In this preliminary study we propose the treatment of the stub surface with a solution based on sodium hypochlorite and calcium chloride, in order to remove/reduce the blood crusts present on the stub surface., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The impact of blood droplets onto a solid wall is of great importance for bloodstain pattern analysis in forensic science. Previous studies suggest that the behaviour of impacting blood is similar to that of a Newtonian fluid, which has a shear viscosity equivalent to that of blood at high shear rates. To understand this important fact, we conducted comparative experiments of droplet impact on a glass surface using whole blood and three solutions with a shear viscosity similar to that of blood. Specifically, we used dog's whole blood (deformable red blood cells dispersed in plasma, WB), plasma with non-deformable resin particles (PwP), glycerol and water with resin particles (GWwP), and a commercial blood simulant (hard particles dispersed in a water-based Newtonian solution, BS). Ranges of Reynolds and Weber numbers in our experiments were 550

The estimated volume of the swing path is referred to as the Path Volume Envelope (PVE) which defines a volume in space from which the path of a blood-releasing object is contained within. FARO Zone 3D is a software program that allows for the calculation of the PVE; however, there are no current studies which look at how well this method performs across various analysts for a simple, human created cast-off pattern. A total of seventeen participants were provided data for a single cast-off pattern that was produced from human motion using a wooden dowel rod as the "weapon". The known three-dimensional motion of the object which created the cast-off pattern was documented using a motion capture system but remained unknown to the participants. The results show that an approximate maximum width of the PVE of±15 cm is enough to encompass the results of all participants in this study. In addition, the X, Y and Z position of the center of the PVE was found to have a standard deviation of 0.1 cm, 5.1 cm, and 9.9 cm, respectively. The standard deviations of the rotations for the PVE around the horizontal and vertical axes (i.e., yaw and pitch) were found to be 2.6° and 1° respectively. Overall, the combined results of all participants were able to fit within a rectangular prism with an overall width of± 15 cm which appears to be a reasonable value for simple scenarios, since it can define an approximate location from where an object was swung relative to a wall or another object at a crime scene. A PVE of greater or lesser maximum width may be required depending on the complexity of the cast-off pattern, the weapon used, and other factors., (Copyright © 2021 Elsevier B.V. All rights reserved.)

There is an apparent paradox that the likelihood ratio (LR) approach is an appropriate measure of the weight of evidence when forensic findings have to be evaluated in court, while it is typically not used by bloodstain pattern analysis (BPA) experts. This commentary evaluates how the scope and methods of BPA relate to several types of evaluative propositions and methods to which LRs are applicable. As a result of this evaluation, we show how specificities in scope (BPA being about activities rather than source identification), gaps in the underlying science base, and the reliance on a wide range of methods render the use of LRs in BPA more complex than in some other forensic disciplines. Three directions are identified for BPA research and training, which would facilitate and widen the use of LRs: research in the underlying physics; the development of a culture of data sharing; and the development of training material on the required statistical background. An example of how recent fluid dynamics research in BPA can lead to the use of LR is provided. We conclude that an LR framework is fully applicable to BPA, provided methodic efforts and significant developments occur along the three outlined directions., (© 2021 The Authors. Journal of Forensic Sciences published by Wiley Periodicals LLC on behalf of American Academy of Forensic Sciences.)

Insects found at a crime scene can produce traces referred to as fly artifacts (FA) due to their movement over the corpse and the manner in which they feed upon it. These can be detrimental for carrying out criminal investigations. Confusing a FA with a genuine bloodspot can lead to misinterpretations, also taking into consideration that FA may contain a human DNA profile. The aim of the present study was to employ scanning electron microscopy (SEM) for the analysis of FA produced by Calliphora vomitoria on hard surfaces and fabrics that are commonly present at crime scenes. FA and control bloodstains were produced under experimental conditions on metal, glass, plaster, cotton, and polyester. After macroscopic analysis, FA were examined at standard low (20-40 ×), medium low (300-600 ×), and high ultrastructural (1200 ×) magnification through a SEM Stereoscan 360, Leica, Cambridge. SEM analysis enabled the identification of distinctive features of FA on hard surfaces, namely, amorphous crystals, micro-crystals with a morphology similar to those of uric or micro-crystals with a comparable morphology to cholesterol, absent in controls. Moreover, red blood cells (RBC) were absent in FA but were always present in controls. On cotton, for both FA and controls, the drop was almost completely absorbed and thus indistinguishable from the underlying fabric texture. On polyester, FA showed amorphous/crystal-like deposits and no RBC, as observed on hard surfaces, except for those showing a completely flat surface. SEM analysis appeared to be suitable for differential diagnosis between FA and genuine bloodstains on hard surfaces, although the results may be inconclusive on tested fabrics., (© 2021. The Author(s).)

Fly artifacts resulting from insect activity could act as confounding factors on a crime scene and interfere with bloodstain pattern analysis interpretation. Several techniques have been proposed to distinguish fly artifacts from human bloodstains based on morphological approach and immunological assay, but a DNA-based method has not been developed so far. Even if in forensic genetic investigations the detection of human DNA is generally the primary goal, fly artifacts can provide useful information on the dynamics of crime events. The present study provides a molecular method to detect fly DNA from artifacts deposited by Calliphora vomitoria after feeding on human blood through the analysis of the mitochondrial cytochrome oxidase gene subunit I (COI). Fly artifacts originated from digestive process and of different morphology spanning from red and brownish/light brown, circular and elliptical stains to artifacts with sperm-like tail or a tear-shaped body were collected. The COI amplification was successfully obtained in 94% of fly artifact samples. The method showed high sensitivity and reproducibility, and no human DNA contamination was observed, offering specificity for use in confirmatory test. This molecular approach permits the distinction of fly artifacts from genuine bloodstains and the identification of fly's species through the COI region sequencing by protocols usually applied in forensic genetic laboratories., (© 2021. The Author(s).)

Blood-drop trajectory analysis can provide investigators with retrospective information regarding the spatial positioning of an injured person. To assist with bloodstain pattern analysis, various commercially available software have been developed and deployed. A systematic review was conducted to understand the extent of experimental validation and applications of blood-drop trajectory analysis software to case work. Ninety-two sources between 1987 and 2020 were identified including peer-reviewed studies and commercial websites. Thirty-four of these were validation studies, of which, only two involved impact patterns generated from greater than 1 m from the main target surface. Fifteen software were identified during this review with six documented to have been applied in casework. The reviewed software do not appear to fully satisfy relevant forensic validation criteria, based on publicly available literature. In some cases, software underwent limited experimental validation prior to real-world application with subsequent references to this in later literature. This review provides forensic investigators and bloodstain pattern analysts with a comprehensive overview of all available software options, knowledge of the extent of research into validating these techniques and highlights documented applications of these software in criminal cases., Competing Interests: Declarations of Interest The authors declare that they have no conflict of interest., (Copyright © 2021. Published by Elsevier B.V.)

Although the analysis of bloodstain pattern evidence left at crime scenes relies on the expert opinions of bloodstain pattern analysts, the accuracy and reproducibility of these conclusions have never been rigorously evaluated at a large scale. We investigated conclusions made by 75 practicing bloodstain pattern analysts on 192 bloodstain patterns selected to be broadly representative of operational casework, resulting in 33,005 responses to prompts and 1760 short text responses. Our results show that conclusions were often erroneous and often contradicted other analysts. On samples with known causes, 11.2% of responses were erroneous. The results show limited reproducibility of conclusions: 7.8% of responses contradicted other analysts. The disagreements with respect to the meaning and usage of BPA terminology and classifications suggest a need for improved standards. Both semantic differences and contradictory interpretations contributed to errors and disagreements, which could have serious implications if they occurred in casework., Competing Interests: Declaration of Competing Interest Authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Mammalian whole blood sources are often used for forensic research and training when human samples cannot be sourced. While porcine, ovine and equine blood have been shown to be viable alternatives to whole human blood for forensic purposes, procurement can still pose a problem, especially for smaller and remote institutions. This work explores the use of whole bovine blood for basic bloodstain simulation. Sample preparation through the addition of ACD-A anticoagulant was optimized and storability was explored. Viscosity, surface tension, density, and packed cell volume, four fluid properties relevant to bloodstain pattern analysis, were monitored over four days and in two temperature conditions. Linear mixed models accounting for variation in the donor demonstrated that these fluid properties of the bovine blood changed predictably over time and with temperature. Whole bovine blood with 12.5% v/v ACD-A was found to be viable for use in basic bloodstain simulation at ambient and physiological temperature., (Copyright © 2021 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.)

In a bloodletting incident, the area of origin (AO) of an impact bloodstain pattern is crucial when establishing the sequence of events. The use of laser scanners and other three-dimensional (3D) technologies to document and analyse bloodstains have been the subject of previous papers, especially where AO analysis is concerned. FARO Zone 3D (FZ3D) is a relatively new software programme that can be used for bloodstain AO analysis. FZ3D requires a greater understanding of inter-observer errors associated with AO. This study looked at the inter-observer variation between 21 examiners when repeatedly calculating the AO six times for a single impact pattern on a plain white wall. An impact rig which consisted of a spring tension arm was positioned and fixed 45 cm from the X wall (right wall), and 45 cm from the Y wall (left wall). This experimental design resembles an impact blow for a bloodletting event. The AO was unknown to all examiners, making it a blind study. The collected results were documented in a Microsoft Excel datasheet and later analysed. From previous literature, a 30 cm acceptable allowance was utilised for AO analysis; however, there is currently no accepted standard error for this type of analysis. The overall total 3D mean error for all examiners was 5.62 cm. The maximum error for any one impact analysis was 24.27 cm. The variation of the data, which was collected by all examiners, was documented as X = 1.14 cm, Y = 1.24 cm, Z = 1.68 cm, and the total 3D error = 2.28 cm. The total 3D error for any one examiner and the variance between examiners did not exceed the 30 cm acceptable allowance utilised in previous literature., (Copyright © 2021 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.)

In the United States, scientific knowledge is brought before the courts by way of testimony - the testimony of scientific experts. We argue that this expertise is best understood first as related to the quality of the underlying science and then in terms of who delivers it. Bloodstain pattern analysis (BPA), a contemporary forensic science, serves as the vaulting point for our exploration of objectivity as a metric for the quality of a science in judicial contexts. We argue that BPA fails to meet the minimal standard set by Helen Longino's social-procedural account of objectivity (1990, 2002). In light of some pressing issues for social-procedural accounts, we offer an infrastructural account of objectivity. This account offers what amounts to a friendly amendment to Longino's account and adds to the ways in which we might analyze social-procedural objectivity. Finally, we address an issue that is pressing in the legal context: given that scientific knowledge is delivered by individuals, not communities, at least in U.S. courts, we (may) need a way to evaluate individual scientific and epistemic agents. We suggest a means for making this evaluation that is derived from our infrastructural account of objectivity.

Cast-off spatter patterns exhibit linear trails of elliptical stains. These characteristic patterns occur by centrifugal forces that detach drops from a swinging object covered with blood or other liquid. This manuscript describes a method to reconstruct the motion, or swing, of the object. The method is based on stain inspection and Euclidean geometry. The reconstructed swing is represented as a three-dimensional region of statistical likelihood. The reconstruction uncertainty corresponds to the volume of the reconstructed region, which is specific to the uncertainties of the case at hand. Simple numerical examples show that the reconstruction method is able to reconstruct multiple swings that are either intersecting or adjacent to each other. The robustness, spatial convergence, computing time of the reconstruction method is characterized. For the purpose of this study, about 20 cast-off experiments are produced, with motion of the swinging object documented using video and/or accelerometers. The swings follow circular or arbitrary paths, and are either human- or machine-made. The reconstruction results are compared with the experimentally documented swings. Agreement between measured and reconstructed swings is very good, typically within less than 10 cm. The method used in this study is implemented as a numerical code written in an open source language, provided in an open access repository, for purposes of transparency and access., Competing Interests: Declaration of Competing Interest There are no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The underlying physics in bloodstain formation on fabrics is not well understood, despite its importance in bloodstain pattern analysis (BPA). This paper presents a fundamental study of the formation of drip bloodstains on fabrics, by focusing on blood droplet impact and wicking dynamics. The bloodstains were created on plain woven fabric by the perpendicular impact of a single blood drop with seven different impact velocities. The whole droplet impact and wicking processes were captured by multiple cameras. Fabric properties were characterized in detail at different levels. The bloodstain formation process was classified into distinct stages, including the inertial impact, initial absorption, first wicking and second wicking stages. The subsequent wicking process greatly alters the impact-induced bloodstains, in terms of bloodstain area. The dimensionless impact-induced stain factor (β i,e ) is strongly dependent on the impact velocity while the final stain factor (β f,e ) after the second wicking stage is not. The contribution of the subsequent wicking in altering the stain factor (or stain area) is quantified and found to decrease with increasing impact velocity. The blood wicking dynamics on the fabric in the majority of the first wicking stage can be well described by a simple scaling: [Formula: see text] , where t i marks the end of the inertial impact stage. The wicking coefficient C, which represents the influence of droplet impact on the subsequent droplet wicking, is found to scale as C∼We -0.34 . In the end, brief comments are provided regarding (1) the influence of the evaporation on the blood drop post-impact wicking dynamics and (2) the shape of bloodstains formed on fabrics, with a few suggested research directions for future work., Competing Interests: Declaration of Competing Interest The authors report no declarations of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Bloodstain pattern analysis, one of the areas of forensic science, is performed to analyze the physical characteristics of bloodstains, including their size, shape, and distribution, to reconstruct a crime scene. A bloodstain pattern analyst should obtain through experiments and education the capabilities to both understand the generation mechanisms of bloodstains and identify the characteristics of the bloodstains. Experiments and education about bloodstain pattern analysis are carried out by using human blood taken from subjects, animal blood (porcine or bovine) supplied from butcheries, and blood substitute products developed in other countries. However, these kinds of blood have many limitations in their application due to various problems. The blood substitute developed in the present study is more similar to human blood than other blood substitute products developed in other countries with regard to the physical properties, including viscosity, viscoelasticity, and surface tension, as well as the drip bloodstain patterns depending on the surface and coordinate characteristics of drip stains impact angle. The blood substitute developed in the present study is more practical, because the materials that are used in its preparation are readily available in the market and do not include chemicals that are harmful to the human body, and the blood substitute has luminol reaction functionality and pattern transfer bloodstain (bloodstain fingerprint, bloodstain footprint, etc.) dyeing functionality., Competing Interests: Declaration of Competing Interest To the best of our know ledge, the named authors have no conflict of interest, financial or otherwise., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

DNA analysts in forensic laboratories are engaged in analysing and sampling bloodstains from bloodstained items. Detailed and precise descriptions of bloodstains on items of interest are very important for bloodstain pattern analysis (BPA). DNA and BPA reports were examined from forensic laboratories in Serbia ( N  = 88). About 400 reports were observed from the past three years. First, we analysed descriptions of items (clothing and shoes) in DNA reports, and special attention was paid to descriptions of bloodstains. Subsequently, we estimated the value of descriptions of bloodstained items of interest in linking specific types of bloodstains to the obtained DNA profiles. Observed descriptions of bloodstained items in DNA reports are usually limited to phrases. A major problem exists in cases where several people were injured in the same bloodshed event. Connecting specific types of bloodstains to obtained DNA profiles is essential for the reconstruction of crime events. The complete analysis should therefore include detailed descriptions of all types of observed and sampled bloodstains. In DNA laboratories that are within a larger institute, it would be more appropriate and productive if BPA and DNA experts examined bloodstained items cooperatively. Moderately sized laboratories have a limited number of employees. So, in those DNA laboratories, it would be more appropriate to educate DNA analysts in the basic principles of BPA.

Cast-off stains are common patterns found at crime scenes involving blood shedding events. However, the analysis and interpretation of cast-off patterns remains an area lacking tools for crime scene investigators. Analyzing cast-off patterns may allow investigators to interpret the area from where an object may have been swung and thus determine the approximate location of a suspect or victim. This study looked at the position and distribution of cast-off patterns and area of origin as a starting point for the development of a method to analyze cast-off patterns. Through a series of tests using a controlled cast-off rig (n = 10), it was observed that a Path Volume Envelope (PVE) may be identified where the swinging path is contained in a volume along with an area of exclusion. The calculated center, linear position of the PVE was found to have an average error of just over 3.2 cm when compared to the known object swing path position. The maximum deviation of the PVE to the known swing path was found to be 5.0 cm with a standard deviation of 1.4 cm. Additional studies are required to investigate the effects of partial cast-off stains, wielded object velocity, direction of swing, distance from the projected surface, and other factors. The observations and analysis from this study were seen to be predictable and repeatable and may provide a possible new method for investigators to interpret cast-off stains., (© 2020 American Academy of Forensic Sciences.)

Previous studies on the storability of porcine blood for bloodstain pattern analysis (BPA) focused on abattoir blood only and did not include measurements of viscoelasticity. Although known to provoke echinocyte formation, EDTA is widely used for BPA issues. We compared ageing samples taken from live pigs with abattoir blood and detected considerable differences in hematocrit (HCT), total protein and shear viscosity that even worsened with time. Upon storage, high shear viscosity continuously increased, resulting in a partial loss of the typical shear thinning property of blood. Furthermore, we explored CPDA-1, the gold standard in preserving red blood cells (RBCs), for storage of forensic samples. We found it to be a superior choice for anticoagulation, as the rise of high shear viscosity was attenuated compared to EDTA. When performing oscillation measurements, we found a sudden change of viscoelasticity of blood after 22 days, providing a cut-off for storage time. To highlight the importance of hematological and hemorheological changes upon cold storage, we performed simple drip pattern experiments. These tests revealed a tendency to smaller stain diameters and higher numbers of satellite spatter. While this contradicts expectations from elevated viscosity values, we associate this trend to microscopic inhomogeneities due to storage. We recommend CPDA-1 for prolonged storage of BPA samples and suggest the use of comprehensive test protocols including viscoelasticity for determination of the maximum shelf life of pig blood., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The forensics discipline of bloodstain pattern analysis plays an important role in crime scene analysis and reconstruction. One reconstruction question is whether the blood has been spattered via gunshot or blunt impact such as beating or stabbing. This paper proposes an automated framework to classify bloodstain spatter patterns generated under controlled conditions into either gunshot or blunt impact classes. Classification is performed using machine learning. The study is performed with 94 blood spatter patterns which are available as public data sets, designs a set of features with possible relevance to classification, and uses the random forests method to rank the most useful features and perform classification. The study shows that classification accuracy decreases with the increasing distance between the target surface collecting the stains and the blood source. Based on the data set used in this study, the model achieves 99% accuracy in classifying spatter patterns at distances of 30 cm, 93% accuracy at distances of 60 cm, and 86% accuracy at distances of 120 cm. Results with 10 additional backspatter patterns also show that the presence of muzzle gases can reduce classification accuracy., (© 2020 American Academy of Forensic Sciences.)

The formation and release under gravity of blood droplets from simulated weapon tips has been investigated experimentally and the results analysed and interpreted using established theoretical models for detached pendent drops. Droplets were produced from a series of conical nozzles, manufactured with a range of cone angles and including a set of un-bored conical tips, under conditions where the tip was either non-wetted or pre-wetted with blood. For the former, radius-limited case, detached droplet volumes were found to agree well with the predictions of both the pendent drop weight and drop shape models. For pre-wetted tips, droplet volumes were found to increase with increasing cone angle and to be independent of whether the blood flow was through an orifice at the tip or across the tip surface itself for un-bored tips. Such angle-limited, detached droplet volumes were predicted well by applying the same contact angle correction factor as for a flat surface. The maximum droplet volume, formed from a horizontal flat surface, was found to be around 150μL for horse blood. Similar theoretical approaches were then extended to droplets released under centrifugal force appropriate to swing cast-off activity and evaluated using previously published experimental data. Order of magnitude agreement for droplet diameters was fairly good but, more importantly, these were found to be proportional to the inverse of the tangential velocity thereby supporting a model where the blood droplet is released directly from a blood mass itself, such as a ligament, rather than from being pinned to some surface feature or orifice on the weapon. This work provides a sound theoretical and experimental understanding of blood droplet release under these conditions that can underpin both future research and the interpretation of blood evidence in case-work., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Bloodstain pattern analysis has a key role in crime scene reconstruction; however, it can be hampered by diverse confounding factors, such as insect activity which may lead to the production of small artifactual bloodstains, commonly referred to as fly artifacts (FA). Although several techniques aimed at distinguishing human bloodstains and FA have been developed, actually, no standardized and reproducible methodology is available. The aim of our study was to test the use of scanning electron microscopy (SEM) to distinguish human bloodstains from FA produced by Sarcophaga carnaria. FA and bloodstains have been produced on five different deposition surfaces under experimental conditions. After visual analysis, bloodstains and FA were analyzed at standard low (× 40-× 300) and high (× 600-× 1200) magnification through a Philips SEM 515. Although differential diagnosis between bloodstains and FA resulted often inconclusive at visual analysis, SEM analysis allowed the identification of additional key distinctive morphological features. In particular, on the surface of FA, small crystal-like and/or amorphous material deposits were observed. Such deposits were absent on bloodstains which, on the other hand, displayed red blood cells stacked in "rouleaux." Basing on these results and under our experimental conditions, SEM analysis resulted suitable to perform a differential diagnosis between bloodstains and FA produced from the insect activity of Sarcophaga carnaria.

In forensic settings, diluted bloodstains are regularly encountered for example when bloodstains are mixed with tap-/rainwater, after deliberate cleaning attempts, or when blood is dropped on a wet surface such as a towel. Such diluted bloodstain scenarios can be subdivided into sequences of events in which a blood drop was either (1) readily diluted (a mixture of blood and water is deposited); (2) deposited on a surface that was readily moistened (first water, then blood) or (3) deposited and subsequently moistened (first blood, then water). Current bloodstain pattern analysis (BPA) lacks data and tools to distinguish these three ways of derivation of a diluted bloodstain that vary in the sequence of deposition of blood and water on textile. In this study, 880 bloodstains were examined for characteristics that can be used to determine the derivation of diluted bloodstains. A guideline to assist BPA-analysts in interpreting diluted bloodstains was extracted. The added value of this guideline was confirmed by conducting two surveys: one survey with and one without the guideline. A third survey confirmed that the characteristics also function on a broader range of textile types that have different weave and knit styles. This guideline can aid BPA-experts to determine, in an objective way, how diluted bloodstains derived which can aid in determining which activities took place at a crime scene., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This comparative study aimed to investigate the differences between the workflow, accuracy, and reproducibility of the area of origin tools in FARO Scene and FARO Zone 3D software. Released in 2018, FZ3D has recently been introduced as an alternative application to FARO Scene's Forensic Wizard plug-in for bloodstain pattern analysis but no accuracy studies have been published at the time of this study. A total of 15 impacts were created using an impact rig at three different positions from two orthogonal walls (50cm, 75cm, 100cm). One researcher conducted the analyses with both software packages, and the total errors using FZ3D were not statistically greater than using FARO Scene (p>0.05). With FZ3D, 50% of the total errors ranged from 6.63cm to 15.68cm with a minimum of 2.45cm, maximum of 27cm, and median of 11.22cm. With FARO Scene, 50% of the total errors ranged from 3.6cm to 15.5cm with a minimum of 2.93cm, maximum of 31.25cm and median of 9.6cm. A blind test with seven participants analyzing the same 15 impacts in FZ3D resulted in 100 out of 105 total errors (95%) to be within the accepted error range of 20cm. Of the five total errors outside 20cm, one was obtained from the 75cm position and four from the 100cm position. 75% of the total errors were below 9.43cm from the 50cm position, 14.88cm from the 75cm position, and 17.39cm from the 100cm position. This could indicate that there is a positive correlation between the distance of the impact from the surfaces and total errors obtained. Based on results of previous literature and comparison to FARO Scene software, FZ3D is shown to have acceptable area of origin analysis tools., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This work characterizes fundamental features of static drip patterns simulated for forensic bloodstain pattern analysis. The purpose of this study was to determine if and how two independent variables, impact velocity and droplet number, influence the parent stain size, shape and satellite spatter distribution of drip patterns created with whole ovine blood. To do this, 500 drip patterns were created in a controlled environment at five varying impact velocities and ten different droplet numbers on a hard paper surface. Digital images of the dried patterns were processed and analyzed using Fiji (ImageJ). The data collected from each pattern support the hypotheses that drip patterns contain predictable and reproducible elements based on impact velocity and droplet number. Basic fluid dynamic principles demonstrate that the size of the parent stains, as well as the number and distribution of satellite stains increase with increasing Weber number. A decrease in the circularity of the parent stains was also noted. This study provides fundamental qualitative and quantitative data on observable elements of drip patterns that can be used practically by bloodstain pattern analysts for pattern identification and classification., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Bloodstain pattern analysis (BPA) is an integral part of crime scene investigation. For violent crimes involving gunshots, standard practice in police departments worldwide have some physical limitations. For instance, the effect of gravity and air drag on trajectories of blood droplets are neglected using current reconstruction methods, which results in a well-known overestimation of the height of the source of blood. As a consequence, more sophisticated models for blood spatter trajectory reconstruction are being developed, two of which are highlighted in the present work. They allow the prediction of bloodstain patterns produced from backward spattered blood droplets from blunt and sharp bullets. Our recent models attribute the splashing of blood to the Rayleigh-Taylor instability which arises when blood is accelerated towards lighter air. This physically-based description comes with the powerful predictive capability to correlate features of bloodstain patterns with the specific bullet and gun that produced them, as well as with the body position. The results of the numerical models were compared with four experiments simulating blood spatter deposition on a vertical wall through the number of stains produced, average stain area, and average impact angle at the surface, and the agreement found is fairly good. Moreover, further insight is obtained by probing and explaining the influence of observable parameters on the resulting spatter pattern, with the goal of aiding BPA experts evaluating a crime scene., (Copyright © 2019 Elsevier B.V. All rights reserved.)

There are few reports of studies of impact spatter on textiles even though bloodstained textiles are found at many violent scenes. Impact spatter was deposited at 90° impact angle onto three knit fabrics of different yarn sizes and on paper. The resulting stain areas and number of stains were measured using ImageJ and compared with stains on paper using one-factor ANOVA. The number of stains observed and their areas on the knit fabrics decreased as the yarn size increased. It was also found that blood that deposited on the fabric wicked only in the direction of the fibers at that location within the fabric which led to distorted stain shapes. Fewer observed impact spatter stains were found on cotton jersey knits for fabrics made with larger yarns than on paper. As the yarn size became smaller, the number of stains became the same as on paper., (© 2018 American Academy of Forensic Sciences.)

The bloodstain pattern analyst sometimes has to judge if a given stain could originate from a specific location. A wide range of values of the maximum distance that a blood drop can travel have been reported from experiments, ranging from less than one meter to more than 10 m. Here we formulate the problem in a fluid dynamics and data mining framework. The fluid dynamics is solved with Newton's classical equation of motion coupled with well-established models for the gravity and drag forces that bend the trajectories of drops. The parameters screened are the drop size, initial velocity and launch angle, as well as the height of a blood source and the ceiling height. Combining a wide range of values of those five parameters commended the performance of more than 5 million fluid dynamic simulations. Results of these simulations have been searched and mined for parameters directly measurable on a crime scene, such as the stain size and stain ellipticity. The results are presented in simple, easy to use charts, which do not require any knowledge of fluid dynamics from the analyst., (Copyright © 2019. Published by Elsevier B.V.)

Trajectory reconstruction in bloodstain pattern analysis is currently performed by assuming that blood drop trajectories are straight along directions inferred from stain inspection. Recently, several attempts have been made at reconstructing ballistic trajectories backwards, considering the effects of gravity and drag forces. Here, we propose a method to reconstruct the region of origin of impact blood spatter patterns that considers fluid dynamics and statistical uncertainties. The fluid dynamics relies on defining for each stain a range of physically possible trajectories, based on known physics of how drops deform, both in flight and upon slanted impact. Statistical uncertainties are estimated and propagated along the calculations, and a probabilistic approach is used to determine the region of origin as a volume most compatible with the backward trajectories. A publicly available data set of impact spatter patterns on a vertical wall with various impactor velocities and distances to target is used to test the model and evaluate its robustness, precision, and accuracy. Results show that the proposed method allows reconstruction of bloodletting events with distances between the wall and blood source larger than ∼1 m. The uncertainty of the method is determined, and its dependency on the distance between the blood source and the wall is characterized. Causes of error and uncertainty are discussed. The proposed method allows the consideration of stains indicating impact velocities that point downwards, which are typically not used for determining the height of the origin. Based on the proposed method, two practical recommendations on crime scene documentation are drawn., (Copyright © 2019. Published by Elsevier B.V.)

Although the characteristics of cast-off bloodstain patterns are well known, the physics of the mechanism by which they are created is poorly understood. The aim of this work was to describe the process by which blood droplets disengage from swinging objects. Cast-off droplets were recorded using high-speed digital video photography, and the resulting cast-off patterns were analyzed to draw inferences about the trajectories of individual drops. Blood on the object's distal end formed ligaments, which subsequently disintegrated into droplets. Initial droplet trajectories were approximately tangential to the trajectory of the location on the object from which the droplet was released. The application of the laws of physics to the mechanism of cast-off is discussed, and the process of drop formation is compared to that of passive drop formation. A technical description of cast-off is proposed, and a diagram to aid investigators in interpreting cast-off patterns at crime scenes is offered., (© 2018 American Academy of Forensic Sciences.)

When conducting a blood pattern analysis (BPA) the size, shape, distribution, and location of bloodstains found at a crime scene may be critical in forming a hypothesis as to what transpired during a bloody event. Prior studies have demonstrated that the size and shape of a bloodstain on a smooth surface are determined from impact dynamics and to a lesser degree by the target material itself. Yet, these studies have relied on clean surfaces, and it is unclear whether the presence of microscopic coatings and residues could significantly alter the size or shape of the dried stain. Here, in the present work, experiments are conducted to demonstrate that various coatings, such as the sebaceous residue from a latent fingerprint, can dramatically alter the size and shape of the stain from the moment of impact through the drying process. These experiments also highlight that a drop impacting a tilted superhydrophobic-coating glass substrate can cause the blood drop to completely recoil without leaving a stain. Relying on a combination of high-speed and time-lapse photography, the specific stages in the stain evolution responsible for the deviations from the current models are identified. At a relatively low impact velocity, the stain sizes on the coated glass surfaces were 35-72% smaller than on the clean glass surface. At a higher impact velocity, the stains on the coated surfaces were not only smaller, but also contained drop spatter around the primary stain that was not observable in the absence of the microscopic coatings. The reduction in bloodstain size did not appreciably change when a chemical was added to deactivate the anticoagulant and allow the blood to clot., (Copyright © 2018 Elsevier B.V. All rights reserved.)

An investigation into the arm and body position required to obtain the blood pattern visible in the image of the Shroud of Turin was performed using a living volunteer. The two short rivulets on the back of the left hand of the Shroud are only consistent with a standing subject with arms at a ca 45° angle. This angle is different from that necessary for the forearm stains, which require nearly vertical arms for a standing subject. The BPA of blood visible on the frontal side of the chest (the lance wound) shows that the Shroud represents the bleeding in a realistic manner for a standing position while the stains at the back-of a supposed postmortem bleeding from the same wound for a supine corpse-are totally unrealistic. Simulation of bleeding from the nail wounds contacting wood surfaces yielded unclear results., (© 2018 American Academy of Forensic Sciences.)

A recurrent observation in forensic casework is that culprits and/or their abettors attempt to remove or mask bloodstain patterns, e.g., by painting the walls. The present study was designed to elucidate whether luminol treatment of bloodstains on (a) plastered and (b) wallpapered walls may help with the visualization of respective patterns after being repainted beyond macroscopic recognition. Furthermore, wallpaper punches of luminol-positive spots were analyzed for DNA. The experiments showed that the prospects for visualization after a four- to sixfold paint application declined considerably as the drying time of the paint increased. A compelling explanation for this observation is that paint becomes increasingly resistant to water during the drying process after paint application. In these cases, moistening the surface in question with distilled water for 15 min has been proven to be a promising pretreatment before luminol application. DNA analysis revealed full STR profiles in 74% of luminol-positive wallpaper punches, whereas rubs of the aforementioned positively tested regions (luminol and human blood pretests) demonstrated negative results.

This study investigates the chemiluminescent reaction of whole ovine blood with a luminol solution in a time and dilution series. Replicate samples of both fresh and dried certified pathogen-free ovine blood were prepared and diluted. Seven dilution conditions from neat to 1:1000000 were created for testing. A luminol solution, created using the standard Weber protocol, was applied to all samples in controlled laboratory conditions. A SpectraMax ® M3 microplate reader luminometer was used to quantify the chemiluminescence from the reactions as relative luminescence units (RLUs) every four seconds for three minutes. Trends within and amongst the times series, reaction half-lives, and maximum chemiluminescent intensities are discussed. Our research provides a comprehensive dataset derived from instrumental and visual observations on the chemiluminescence resulting from ovine blood's reaction to luminol. This study has implications in forensic bloodstain pattern analysis as it offers a mixed method approach to characterizing the reaction between blood and a commonly used presumptive testing reagent., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A backspatter pattern results from blood drops that travel retrograde to an applied external force. Historically, an array of animals and nonhuman objects have been used to create and study backspatter patterns. In this study, backspatter patterns captured on foam core targets that were placed 45.72 cm (18 in) behind the impact site (occipital area of the skull) were produced by cranial gunshots to human cadavers that were reinfused with fresh defibrinated bovine blood. These patterns were compared to the backspatter patterns produced by shooting blood-soaked sponges, a typical simulant used in controlled studies of backspatter pattern production and characteristics. The backspatter pattern produced by shooting an actual human head was found to be different than those of blood-soaked sponges in the number of stains produced, the size and size range of the stains, and the stain dispersion patterns., (© 2017 American Academy of Forensic Sciences.)

In the forensic discipline of bloodstain pattern analysis, it has been suggested that there is a blurred boundary between characterising the features of a bloodstain pattern and determining the mechanism(s) that led to its deposition. This study proposes that bloodstain pattern classification can become a distinct and logical process by implementing an automated approach. To do this, an automated bloodstain pattern recognition system was developed to enable the distinction of two types of spatter bloodstain patterns. First, global pattern features based on common bloodstain pattern properties were extracted from laboratory-generated impact spatter and cast-off bloodstain patterns. Following this, automated feature selection methods were used to identify the combination of features that best distinguished the two bloodstain pattern types. This eventually led to the training and testing of a Fisher quadratic discriminant classifier using separate subsets of the generated bloodstain patterns. When applied to the training dataset, a 100% classification precision resulted. An independent dataset comprising of bloodstain patterns generated on paint and wallpaper substrates were used to validate the performance of the classifier. An error rate of 2% was obtained when the classifier was applied to these bloodstain patterns. This automated bloodstain pattern recognition system offers considerable promise as an objective classification methodology which up to now, the discipline has lacked. With further refinement, including testing it over a wider range of bloodstain patterns, it could provide valuable quantitative data to support analysts in their task of classifying bloodstain patterns., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This article describes a New Zealand forensic agency's contextual information management protocol for bloodstain pattern evidence examined in the laboratory. In an effort to create a protocol that would have minimal impact on current work-flow, while still effectively removing task-irrelevant contextual information, the protocol was designed following an in-depth consultation with management and forensic staff. The resulting design was for a protocol of independent-checking (i.e. blind peer-review) where the checker's interpretation of the evidence is conducted in the absence of case information and the original examiner's notes or interpretation(s). At the conclusion of a ten-case trial period, there was widespread agreement that the protocol had minimal impact on the number of people required, the cost, or the time to complete an item examination. The agency is now looking to adopt the protocol into standard operating procedures and in some cases the protocol has been extended to cover other laboratory-based examinations (e.g. fabric damage, shoeprint examination, and physical fits). The protocol developed during this trial provides a useful example for agencies seeking to adopt contextual information management into their workflow., (Copyright © 2018 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.)