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Objectives: Heat exposure can lead to apparently random osteometric changes that hinder the application of metric methods used for biological profiling. The impracticality of using objective and burn-specific osteometric methods reduces the chances of establishing the biological profiles of unknown individuals based on their skeletal remains. We investigated the potential of chemometry analysis based on infrared spectroscopy to predict the amount of heat-induced osteometric changes and how this reflected into sex estimation., Material and Methods: Bones from 41 identified adult skeletons (24 females and 17 males with ages between 62 and 90 years old) were experimentally burnt to maximum temperatures ranging from 450°C to 1,100°C (attained after 65 to 240 min). Measurements were taken both before and after each experiment and powder samples were analyzed through FTIR-ATR. Correlations among heat-induced metric changes and chemometric indices (crystallinity index; B-type carbonates; carbonate [A + B] to carbonate B ratio; hydroxyl to phosphate ratio; 630 cm -1 , 1450 cm -1 , 3572 cm -1 , and 3642 cm -1 ) were tested. Significant variables were used to build regression models to predict heat-induced metric change which were then tested on an independent set of samples. Agreement in sex estimation between the pre- and post-burnt samples was also evaluated., Results: All indices were significantly correlated to heat-induced metric changes (α = .01) and the highest correlations were obtained for the 630 cm -1 , 3572 cm -1 , and crystallinity index. We confirmed that regression models based on chemometrics obtained from infrared spectra through FTIR-ATR are better at estimating heat-induced metric changes affecting bone and at sexing remains than other osteometric methods such as those based on correction factors or on metric references specific to calcined bones., Discussion: Regression models avoid the subjectivity associated with the application of other methods. While the latter can be applied only to calcined bones, which is difficult to assess sometimes, regression models can be applied to all bones regardless of their condition. Also, regression models have the advantage of allowing to infer about heat-induced metric change on a case-by-case basis., (© 2020 Wiley Periodicals LLC.)

In forensics, assessing the pre-burning condition is important to determine the circumstances of death. Heat-induced warping (HIW) occurs more frequently on non-dry bone but is not a reliable indicator of the pre-burning condition of human remains. Several factors have a significant effect on warping (e.g. maximum temperature) but others are still unknown. We investigated the effect of Earth's force of gravity on HIW by experimentally burning 23 human long bones from 4 different unidentified skeletons at different temperatures. Only 56% of the warped bones (n = 16) presented HIW compatible with gravity. These bones presented larger masses than the bones presenting warping incompatible with gravity, thus suggesting that bone mass plays a role in HIW. Probably, the intrinsic contractile forces caused by heated collagen are at the origin of warping and such bending may be compatible with gravity depending on bone mass. Possibly, incompatibility occurs when intrinsic bending is counteracted by gravity whenever bone mass produces a stronger force. We therefore conjecture that HIW results from a combination of at least two different forces. HIW is multifactorial and finding a reliable indicator of the pre-burning condition of human remains may be only possible at the microscopic and elemental levels. [ABSTRACT FROM AUTHOR]