Sgt Paul Cortez admitted four murders, rape and conspiracy to rape. His plea
meant he avoided the death penalty.
He received a dishonourable discharge and will be eligible to seek parole in 10
years.
In November, Specialist James Barker, 24, admitted rape and murder over the
killings and was jailed for 90 years.
In court on Thursday, Cortez broke down as he confessed to raping the girl as
her parents and sister were shot dead in another room.
The case is one of several in which US troops are accused of killing Iraqis.
According to the plea agreement, Cortez admitted conspiring with three other
soldiers, Private First Class Jesse Spielman, Specialist Barker and Steven
Green, a now discharged soldier, to rape Abeer Qassim al-Janabi.
Card game
Pte Spielman and another man, Bryan Howard, are awaiting court martial on
charges related to the attack.
"Green came out of the bedroom and said that he had killed them all, that all
of them were dead," said Sgt Paul Cortez.
US Iraq inquiries
Mr Green is being tried as a civilian because he was discharged from the army
before his superiors knew of his suspected involvement. He denies the charges
against him.
All five belonged to the 101st Airborne Division based at Fort Campbell,
Kentucky, which is also where the hearing took place.
In court, Cortez admitted the plan was hatched as they played cards and that
the girl had been targeted because there was only one male in her house, making
it an easy target.
