600 Americans abused detainees: HR group

The three groups who researched what they called "widespread" torture and detainee abuse by US personnel said many abuses were never investigated, or inquiries were often concluded or stalled without further action.

"Two years ago, US officials said the abuses at Abu Ghraib were aberrations and that people who abused detainees would be brought to justice," said Meg Satterthwaite of New York University's Center for Human Rights and Global Justice, one of the groups behind the study.

"Yet our research shows that detainee abuses were widespread, and few people have truly been brought to justice," Satterthwaite said.

The research project, also backed by Human Rights Watch and Human Rights First, examined allegations of mistreatment involving more than 460 detainees at Iraq's Abu Ghraib prison, sites in Afghanistan and the Guantanamo camp in Cuba.

They found that "many abuses were never investigated, and investigations that did occur often closed prematurely, or stalled without resolution," said a summary of the report.

Where abuses were proven and the perpetrators known, the report said, "military commanders often chose to use weak non-judicial disciplinary measures as punishment" instead of pursuing criminal cases.

"Only a fraction of the more than 600 US personnel implicated in these cases -- 40 people -- have been sentenced to prison time," the report said.