"We found no link between approved interrogation techniques and detainee abuse," the review concluded.
The review led by Navy Vice Adm Albert T Church did cite a number of "missed opportunities" in the development of interrogation policies, according to a 21-page executive summary of his findings due to be publicly released on Thursday.
Among the missed opportunities was a failure to provide commanders in Iraq and Afghanistan with specific and early guidance on interrogation techniques.
"We cannot say that there would necessarily have been less detainee abuse had these opportunities been acted upon," Church wrote.
Had that guidance been provided earlier, "interrogation policy could have benefited from additional expertise and oversight," he wrote.
More restrictive policy
The Church report also disclosed that the top US commander in Iraq, Army Gen George Casey, who arrived there last summer, approved on 27 January a new, more restrictive interrogation policy for Iraq.
Casey's policy, which previously had not been made public, "also provides additional safeguards and prohibitions, rectifies ambiguities" and requires that commanders report to Casey their compliance with the policy, the report said.
"We found no link between approved interrogation techniques and detainee abuse"
The investigation also found, in the cases of detainee operations in Iraq and Afghanistan, that the dissemination of approved interrogation policy to commanders in the field was generally poor. And in Iraq it found that compliance with approved policy guidance was generally poor.
By contrast, the report said that compliance with the authorised interrogation methods was in nearly all cases exemplary at Guantanamo Bay, where "terrorism suspects" have been held since January 2002. It attributed this to strict command oversight and effective leadership, as well as adequate resources.
Abu Ghraib effect
The Church investigation was among several triggered by disclosures last spring of prisoner abuse at the Abu Ghraib prison complex in Iraq. Church, formerly the Navy's chief investigator, was directed to look at how interrogation policies were developed and implemented from the start of the "terror war" in the fall of 2001.
"An early focus of our investigation was to determine whether DOD (the Department of Defence) had promulgated interrogation policies or guidance that directed, sanctioned or encouraged the abuse of detainees. We found that this was not the case," the Church investigation concluded.
The Abu Ghraib scandal triggered
a number of abuse investigations
"Even in the absence of a precise definition of `humane' treatment, it is clear that none of the pictured abuses at Abu Ghraib bear any resemblance to approved policies at any level," it added.
Church did not directly investigate the Abu Ghraib matter or address questions about accountability for senior defence officials involved in interrogation policy.