Washington ( CNN ) -- New documents obtained by the American Civil Liberties Union show `` unjustified homicide '' of detainees and concerns about the condition of confinement in U.S.-run prisons in Iraq , Afghanistan and Guantanamo Bay , according to the ACLU . Thousands of documents detailing the deaths of 190 U.S. detainees were released by the ACLU on Friday . The U.S. military gave the ACLU the documents earlier in the week as a result of a Freedom of Information Act ( FOIA ) lawsuit filed by the rights group . Among the documents are autopsy reports and military investigations , including 25 to 30 cases the ACLU says it believes are `` unjustified homicide . '' Some of the homicides in the documents are widely known and have been reported in the media , such as the case of four Iraqi detainees executed by a group of U.S. soldiers and then pushed into a Baghdad canal in 2007 . Others are thought by the ACLU to be new . In one such case , a detainee was killed by an unnamed sergeant who walked into a room where the detainee was lying wounded `` and assaulted him ... then shot him twice thus killing him , '' one of the investigating documents says . The sergeant than instructed the other soldiers present to lie about the incident . Later , the document says an unnamed corporal then shot the deceased detainee in the head after finding his corpse . In another example , documents note a soldier `` committed the offense of murder when he shot and killed an unarmed Afghan male . '' But , according to the ACLU , the individual was found not guilty of murder by general court-martial . `` So far , the documents released by the government raise more questions than they answer , but they do confirm one troubling fact : that no senior officials have been held to account for the widespread abuse of detainees . Without real accountability for these abuses , we risk inviting more abuse in the future , '' the ACLU said in a statement . The Defense Department disputes the allegations , saying it takes detainee treatment seriously . `` DoD policy requires the immediate reporting of detainee deaths to appropriate DoD criminal investigative agencies regardless of the circumstances at the time of death , '' said Pentagon spokeswoman , Lt. Col. Tanya Bradsher . `` Indeed , the fact that so many autopsies and investigative reports exist indicates the seriousness with which the Department takes its responsibilities regarding detainee treatment and accountability . '' Of the investigations in the documents , 43 had U.S. soldiers or personnel as potential suspects , according to Lt. Col. David H. Patterson , an Army spokesman . Probable cause for murder was found in 13 of those investigations , resulting in 19 separate convictions , Patterson said , many of which carried significant sentences , with some soldiers receiving 20 years or more . `` It 's important to remember that the majority of these detainee deaths were due to reasons not directly involving U.S. personnel . For example , a number were the result of detainee-on-detainee violence , '' Patterson said . `` Although there have been cases of individuals involved in misconduct , there is no evidence of systematic abuse by the United States military , '' said Bradsher . `` The ( Defense ) Department has detained more than 100,000 individuals in Iraq and Afghanistan , many with pre-existing medical conditions or battlefield wounds . Detainees in DoD custody have died from a number of causes including enemy attacks , detainee-on-detainee violence , battlefield injuries , and natural causes . '' One concern noted by the ACLU is the amount of deaths that involved cardiac problems : over 25 % . The group says it is looking into this finding . `` This could potentially raise serious questions about the conditions of confinement or interrogation of the detainees , '' the ACLU said . The ACLU obtained the 2,624 pages of documents through a Freedom of Information Act request filed with the government in 2009 . The package included about 124 autopsy and 133 investigation reports .
Documents show `` unjustified homicide '' of detainees , ACLU says . The documents were released to the rights group by the U.S. military . The Defense Department says it takes detainee treatment seriously .