Military investigators recommended courts martial for the soldiers in the cases of three prisoner deaths for charges ranging from making false statements to murder.
Officers rejected those recommendations, ruling that the soldiers lawfully used force or did not understand the rules for using force, or that there was not enough evidence to prosecute.
Eleven US Army soldiers are facing murder or other charges involving the deaths of detainees in Iraq or Afghanistan.
The Army Criminal Investigation Command released a report on Friday detailing the cases of 27 detainees killed in custody in Iraq and Afghanistan between August 2002 and November 2004.
Twenty-four cases encompassed the 27 deaths; 16 investigations have been closed and eight remain open, according to the report.
Five cases were referred to other agencies, including deaths involving naval and marine troops as well as CIA operatives.
"We take each and every death very seriously and are committed and sworn to investigating each case with the utmost professionalism and thoroughness," said Chris Grey, a spokesman for the Criminal Investigation Command.
Army investigators turn over their recommendations to commanders of the soldiers involved when they finish their investigations. Those commanders can decide whether to bring criminal charges against the accused soldiers.
In one case, commanders decided not to file recommended criminal charges against 11 soldiers involved in the death of a former Iraqi army lieutenant-colonel in January 2004.
"We take each and every death very seriously and are committed to investigating each case"
US Army criminal investigator
An autopsy indicated the man died from blunt force injuries and asphyxia. Investigators determined there was enough evidence for negligent death charges against two soldiers and for lesser charges, ranging from making false statements to assault, against nine others.
The accused soldiers' commander, however, decided that the soldiers were justified in using force against the Iraqi because he was being aggressive and misbehaving. The case is closed.
In another case, Special Forces commanders decided not to bring charges against a soldier accused of shooting and killing a detainee in Afghanistan in 2002.
The Special Forces commanders decided there was not enough evidence to bring that soldier to trial, the New York Times reported on Saturday.
The third case involved a soldier who killed an Iraqi detainee in September 2003. That soldier's commander decided the soldier was not well informed about the rules for using force against prisoners.
One case where soldiers are facing courts martial involves the death of a former Iraqi army major-general who was stuffed headfirst into a sleeping bag and suffocated. Four soldiers from the 3rd Armoured Cavalry Regiment are awaiting trial on murder charges at Fort Carson, Colorado, in that case.
Another case involves three killings in the Sadr City sector of Baghdad in August 2004, all involving soldiers from the 1st Cavalry Division who allegedly shot Iraqis during search operations.
The report looked at US Army
conduct in Iraq and Afghanistan
Two soldiers in this case have pleaded guilty at courts martial and charges against two other soldiers are pending courts martial.
In one of the Sadr City cases, two 1st Cavalry soldiers have been convicted of murder. One is Staff Sergeant Johnny Horne of Winston-Salem, North Carolina, who pleaded guilty to killing a critically wounded 16-year-old Iraqi on 18 August 2004.
Horne described it as a mercy killing. He was sentenced to three years in prison, a reduction in rank to private, total forfeiture of wages and a dishonourable discharge.
The other soldier convicted in the same killing was Staff Sergeant Cardenas Alban of Inglewood, California. He was sentenced to one year in prison, a bad-conduct discharge from the army and reduction in rank to private.
Another 1st Cavalry soldier faces charges of murder and obstruction of justice in the deaths of two other Iraqis who were killed while being detained during the same August 2004 operation in Sadr City.
Still another soldier faces charges of murder and making a false statement about one of those two deaths. The involvement of other soldiers is still under investigation.