A Northern Virginia military police soldier who served at Abu Ghraib prison in Iraq has pleaded guilty to one charge of dereliction of duty, accepting responsibility for not preventing or reporting detainee abuses at the hands of other U.S. soldiers in her company, according to her civilian lawyer and military officials in Iraq.

Megan Ambuhl, 30, of Centreville, entered her plea Saturday in Baghdad as part of a deal with prosecutors, who agreed to drop charges of conspiracy, maltreatment of detainees and indecent acts. In a summary court-martial, which spared her the possibility of a lengthy prison term, Ambuhl was sentenced to a reduction in rank from specialist to private and was ordered to forfeit half of one month's pay, according to a military spokesman in Iraq.

Ambuhl became the third soldier from the 372nd Military Police Company to plead guilty to charges connected with the scandal that broke in April after photographs of detainee abuse surfaced. One soldier was sentenced to a year in prison, and another to eight years.

According to investigative documents, Ambuhl was the least involved in the abuse of the seven soldiers who have been charged so far. She was accused in large part of watching abusive acts and failing to report them.

Harvey Volzer, Ambuhl's Washington-based civilian attorney, said yesterday that his client witnessed some abusive acts on Tier 1 of the prison but did not report them because her superiors were involved and military intelligence soldiers appeared to be sanctioning the acts. Volzer said Ambuhl regrets not doing something to stop the abuses and shows remorse.

"I think we all came to the conclusion that my client didn't hit or kick a detainee or anything like that," Volzer said, "but everyone had a duty to protect the detainees, and even if this was authorized from above, in some instances it went too far."

According to investigative documents, Ambuhl was present when sexual abuses occurred in the prison's most secure wing, including episodes when soldiers placed naked and hooded detainees into a pyramid and then posed with them for photographs. She is also partially visible in a photograph that showed Pfc. Lynndie R. England holding a leash attached to a naked detainee's neck.

Ambuhl was praised by several detainees for treating them well, and in at least one instance she came to the aid of a detainee who was having trouble breathing after being punched in the chest by another soldier, the documents showed.

Volzer said Ambuhl's punishment is appropriate because of her limited involvement, but he said he is dismayed by the lack of accountability for higher-ranking officials who he says condoned the abusive treatment.

"My position is that if people order you to do things and you do what they said, and as a result you're punished, the people who gave the orders should also be punished," Volzer said. "Since the orders came down from the White House, someone has to bear responsibility for it."

Volzer said Ambuhl is prepared to testify at other military proceedings. Additional courts-martial for those involved in the abuses are scheduled to begin early next year.

Ambuhl, who was supposed to have returned home from duty last summer, is expected to return within the next two weeks. Volzer said Ambuhl plans to leave the military and to return to her job as a lab technician.

Staff writers Jackie Spinner in Iraq and Elizabeth Williamson contributed to this report.