During the twentieth century, hundreds of thousands of people have been victims of extrajudicial executions worldwide, in episodes of violence associated with armed conflicts, political repression and ethnic cleansing (Shelton 2005). From the crimes committed during the Second World War, to the political repression in dictatorial regimes in Latin America (e.g. Chile, Argentina, Guatemala) and east Asia (e.g. Cambodia), to the recent conflicts in the former Yugoslavia, central Africa and the Middle East, in most of these cases the victims of the killings have been illegally buried in clandestine mass graves. In this context, we define a mass grave after the definition provided by the United Nations special rapporteur to the International Criminal Tribunal for the Former Yugoslavia (ICTY) as a location where three or more bodies are buried, victims of extra-judicial, summary or arbitrary executions, not having died in combat or armed confrontations (ICTY 1996). In many cases, forensic projects have been organized in order to exhume and identify theremains of the victims from these mass graves. The main immediate objectives of these forensic projects have been the return of the remains to the families and/or the collection of evidence to establish accountability and bring those responsible to justice (although in all cases there should be an ethical and practical commitment for personal identification of the remains). More generally, the information obtained from these projects, together with information obtained from interviews of survivals, relatives of the victims, witnesses and perpetrators, fulfil the role of a public recognition of the episodes of violence and reaffirmation of the dignity of the victims, with the twofold objective of avoiding denial of those episodes and of their divulgation for a critical rejection of violence (Haglund 2002). Some of the earliest exhumations of mass graves were related to the Second World War,1for example those carried out at Katyn (Russia), where thousands of officers of the Polish armywere executed and buried in mass graves by members of the Soviet Army in 1940. Subsequently, the Nazi Army (1943) and the Soviet Army (1944) carried out exhumations of these graves, although the main objective of both projects was to collect evidence of the killings for accusing the opponent (Taylor 1992). Legally, the search for systematic crimes against civil population goes back to the Hague Conventions of 1899 and 1907 (including the Martens Clause that provided the distinction between combatant and non-combatant populations), the Leipzig War Crime Trials after the First World War, and especially the Nuremberg and Tokyo Trials after the Second World War, which used large-scale forensic evidence for the prosecution of war crimes. The reconstruction of international relations after Second World War resulted in the foundation of the United Nations and Resolution 95-I of 1946, which consolidated the notion of crimes against humanity and notion of crimes of war (Ball 1999; Capella 2011; Valencia 2011). With regard to the exhumation of mass graves, the next significant advance came with the denunciations of crimes committed by the Latin American dictatorial regimes during the 1970s and 1980s, and the subsequent foundation in 1984 of the first forensic team dedicated to the search of missing persons, the Argentinian Team of Forensic Anthropology (Doretti and Snow 2003). After this initiative followed the development of the first protocol for the investigation and prevention of arbitrary executions and documentation of torture (United Nations 1991), the investigation of mass graves from the Second World War in Ukraine in 1990 (Bevan 1994) and especially the implementation by United Nations of the International Criminal Tribunal for the former Yugoslavia in 1993, and the International Criminal Tribunal for Rwanda in 1994, both of which have made extensive use of the information obtained from the exhumation and analysis of human remains from mass graves. During the 1990s, diverse national (e.g. Guatemala, Peru) and international (e.g. United Nations, Physicians for Human Rights, International Commission for Missing Persons) forensic teams were created and exhumations of mass graves have been carried out worldwide by these and other teams, with bioarchaeologists playing an important role alongside forensic pathologists and other professionals (Skinner et al. 2003; Skinner and Sterenberg 2005). This brief summary of the killings involving civil populations and their subsequent investiga-tion during the twentieth century should include Spain. On 18 July 1936, a fascist coup promoted by a faction of the Spanish army was carried out against the elected government of the Spanish Republic, unleashing a civil war that lasted three years (1936-9) and ended in an extreme right-wing dictatorship led by General Franco, who remained in power until his death in 1975. It has been estimated that during the Spanish Civil War and the first ten years of the dictatorship that followed, at least 175,000 people were killed away from the battlefield, most of them buried in mass graves. This number refers to “violent deaths away from the frontline, excluding bombing of defenseless cities. Victims of paseos, sacas, shootings at the walls of cemeteries, executions carried out by death sentences from martial courts or popular tribunals” (Julia 1999: 407-14). Unlike other cases of systematic human rights violations, these crimes have not been officially investigated by any legitimate Spanish government, commission or court, and the investigation of the pattern of violence exerted in the territories controlled by both sides has been conducted by historians (Julia 1999; Espinosa 2009, 2012; Preston 2012). One of the most recent investigations indicate that the Republican violence had cost the lives of 49,000 people, while the Francoist violence had cost the lives of at least 127,000 (Preston 2012). Consistent with this lack of official investigation, there has been no official forensic exhumation project of the mass graves. Nevertheless, exhumations of mass graves occurred during the immediate post-war period, promoted by the dictatorship in order to identify victims of Republican violence, and during the last years of dictatorship and the transition to democracy (1975-82), when hundreds of exhumations were carried out to recover the victims of Francoist violence by the familiesthemselves, without any state support (e.g. Aguirre 2008). These exhumations declined after the attempted coup of 23 February 1981, but in 2000 a Spanish journalist searching for his grandfather contacted an archaeologist, a physical anthropologist and a forensic doctor, who carried out the first exhumation of a mass grave from the Spanish Civil War using archaeological methods (Silva and Macias 2003). The remains of 13 persons were exhumed and the grandfather of the journalist was identified. That exhumation sparked a large number of requests for exhumations and – according to a database managed by the Society of Sciences Aranzadi (Donostia, Basque Country), the purpose of which is to compile basic data from the exhumations carried out in Spain – to date 330 mass graves have been exhumed and 6,174 remains have been recovered at the request of families of Republicans, with the objective of identify the remains and burying them in a legal and dignified place. The lack of a legal instrument to deal seriously with the investigation of the human rights violations that occurred in Spain during the civil war and the dictatorship has resulted in the absence, or partial support, of the Spanish public administrations to the exhumations. The responsibility for this task has been delegated to the families of the victims, who have personally contacted professionals from different disciplines to carry out the exhumation and identification process. In this highly criticized model of exhumations (Escudero 2011), our team has participated in more than 50 exhumations of mass graves from different Spanish provinces, and the results of our main objective – the identification and return of the remains to the families – has been described elsewhere (Rios et al. 2010, 2012; Etxeberria et al. 2012). As previously mentioned, the main objective of the exhumations of victims of systematichuman rights violations should be the identification of the remains, but as indicated by TidballBinz (2008: xii), the International Committee of the Red Cross (ICRC) recommended a focus “on the proper recovery, management and identification and human remains, with the understanding that this is as important as establishing the cause, manner, and circumstances of death of the deceased”. Furthermore, Baraybar and Gasior (2006: 103) explained that “the analysis of the signs of peri-mortem trauma by the anthropologist ultimately leads the pathologist to make a determination as to the individual’s cause of death, which is vital to the prosecution of war crimes”. As explained above, there is no such investigation or prosecution of these crimes in Spain, and our skeletal analysis is focused on the identification of the remains, but we also proceed to a detailed study of the peri-mortem trauma as a mandatory part of our report in order to provide as much information as possible with regard to the clarification of the cause, manner and circumstances of death, as well as to leave a record that may be useful for professionals working in other cases of systematic violations of human rights. The objective of this chapter is therefore to present the first systematic description of the peri-mortem trauma observed in skeletons exhumed from mass graves from the Spanish Civil War.