Frederick, 38, of Buckingham, Va., admitted to allegations of conspiracy, dereliction of duty, maltreatment of detainees, assault, and committing an indecent act. He was expected to be sentenced Thursday.
Frederick, a military policeman and a corrections officer in civilian life, is the highest-ranking soldier charged in connection with the Abu Ghraib prisoner scandal, which broke in April with the worldwide publication of photos and videos showing American soldiers abusing and humiliating naked Iraqi detainees.
Under a plea bargain deal, several other charges against Frederick were dropped, according to his attorney Gary Myers.
Frederick is the highest-ranking member of the 372nd Military Police Company charged in the scandal. Six others from the Cresaptown, Md.-based unit also were charged; one, Spc. Jeremy C. Sivits, of Hyndman, Penn., is serving a one-year prison sentence after pleading guilty in May to three counts.
Frederick is alleged to have watched as a group of detainees were made to masturbate while other soldiers photographed them. He also is accused of jumping on a pile of detainees, stomping on detainees' hands and bare feet, and punching one in the chest so hard he needed medical attention.
In addition, Frederick allegedly helped place wires in a detainees' hands and told him he would be electrocuted if he fell off a box.
The proceeding includes witness testimony and other evidence but almost all the witnesses will participate by video teleconference from outside Iraq, Frederick's lawyer said.
Several of the defense witnesses will be in Washington or Europe. One of the government's two witnesses also will testify remotely, from Mannheim, Germany.
The unusual arrangement ensured better cooperation from witnesses who were afraid to visit a war zone after a military appellate court refused to move the proceeding out of Iraq, according to Myers.
Frederick's wife, Martha, is on Myers' witness list. "I don't think anybody in their right mind would be willing to go to Iraq," she said.
Since the photographs depicting abuse at Abu Ghraib surfaced, attorneys for the accused soldiers have claimed higher-ranking officers were involved. Much of the investigative work has focused on the question of whether intelligence officers, Pentagon officials or their policies were to blame.
One Army investigation found that twenty-seven members of an intelligence unit at Abu Ghraib either requested or condoned certain abuses of Iraqi prisoners there.
Of the 27 individuals, 23 were members of the military personnel and four were contractors. Another eight, including two contractors, knew of abuse and failed to report it, the report said.
It blamed the abuses on several factors: "misconduct (ranging from inhumane to sadistic) by a small group of morally corrupt soldiers and civilians, a lack of discipline on the part of leaders and soldiers," and a "failure or lack of leadership" by higher command in Iraq.
Some of the abuses during interrogations were committed by soldiers who were unclear on what techniques they could legally use on prisoners, the report says.
A separate report found that inattention to prisoner issues by senior U.S. military leaders in Iraq and at the Pentagon was a key factor in the abuse scandal, but there is no evidence they ordered any mistreatment.
The four-member commission appointed by Defense Secretary Donald H. Rumsfeld and headed by former Defense Secretary James R. Schlesinger directly blamed the events at Abu Ghraib on the soldiers there and their immediate commanders.
It also said senior commanders and top-level Pentagon officials, including Rumsfeld, can be faulted for failed leadership and oversight.
Schlesinger's review criticizes senior leaders for not focusing on issues stemming from the detention of large numbers of prisoners in Iraq. This lack of attention and resources contributed to the chaotic conditions at Abu Ghraib, the report said.
In particular, war planners at the Joint Chiefs of Staff did not expect a widespread anti-U.S. insurgency or the breakdown of civil order in postwar Iraq, so they did not plan or provide resources for the operation of a large American-run prison system, commissioners said.
Nor did senior leaders fully clarify what interrogation methods were permissible at Abu Ghraib. In some cases, harsher techniques approved for use against al Qaeda and Taliban fighters were employed against Iraqi prisoners.
The Schlesinger report assigned significant blame to Lt. Gen. Ricardo Sanchez, the top U.S. commander in Iraq, saying he should have ensured that his staff dealt with the command and resource problems at Abu Ghraib when they first came to light in November 2003. Still, it acknowledges that Sanchez was focused on combating a mounting Iraqi insurgency at the time.
Schlesinger said soldiers who stacked naked Iraqi prisoners in pyramids, forced them into positions of sexual humiliation and confronted them with snarling guard dogs were renegades.
The abuse depicted in the Abu Ghraib photographs made public was "a kind of 'Animal House' on the night shift," Schlesinger said -- in other words, acts of sadism committed by low-ranking guards for their own entertainment.
The report described the abuse as "acts of brutality and purposeless sadism," and said -- as have others who reviewed the case -- that the soldiers involved were not acting on approved orders or policies.
On the other hand, the report contradicts the Bush administration's assertion that the problem was limited to a few soldiers acting on their own. So far, seven military police soldiers have faced criminal charges; two dozen or more military intelligence soldiers may also be charged, but it appears increasingly unlikely that top-level commanders will be disciplined.
About a third of 66 substantiated cases of abuse were committed during interrogations, presumably by military intelligence personnel or people working with them, the Schlesinger report said. At least five prisoners died as a result of abuses committed during questioning. Twenty three deaths - three in Afghanistan and the rest in Iraq - are still under investigation.