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Since his October 2002 arrest, Lee Boyd Malvo has vacillated between anger at his accomplice in the sniper spree that left 10 people dead and loyalty to the man who accepted him as a son.

This week, Malvo may give the world an account of where he stands when he is expected to testify for prosecutors against John Allen Muhammad, the man who allegedly molded him into a ruthless 17-year-old sniper.

Muhammad, already convicted of a sniper killing in Virginia and sentenced to death, is on trial now for the six homicides in Montgomery County during a three-week rampage that terrorized the Washington area. Malvo has been convicted of a sniper killing in Virginia and was sentenced to life in prison.

Malvo is expected to plead guilty to the Maryland charges against him and testify for prosecutors, according to a person close to the case who spoke on condition of anonymity because the deal was not final. Neither Malvo's attorney, Tim Sullivan, nor Montgomery County prosecutors would comment; a gag order is in place.

Malvo's testimony, which could come as early as Monday, will be particularly compelling because no one knows exactly what he will say.

Shortly after his arrest, Malvo confessed to being the triggerman in all the shootings. But he later recanted and told mental health experts hired by his lawyers that Muhammad, 45, was the shooter in nearly all the deaths.

Malvo's court-appointed lawyers in Virginia have said that Malvo also changed his mind frequently about his feelings toward Muhammad, even more than a year after the two were arrested and separated.

Malvo's lawyers contended Muhammad brainwashed the teenager and turned him into a killer, and that Malvo never fully separated himself from Muhammad, despite being angry about the path on which Muhammad led him.

Muhammad, meanwhile, continues to view Malvo as his son, frequently referring to him as such during the Maryland trial.

Muhammad promised in his opening statement that he would prove not only his innocence but Malvo's. Muhammad described how Malvo saved his son, John Jr., from drowning on a Caribbean beach.

"Ever since then, I swore to Lee — my son Lee Boyd Malvo — and my children, that I would always protect them," Muhammad said.

He went on to say that he and Malvo came to Washington, D.C., in October 2002 to look for Muhammad's children, whom he had lost in a custody battle. When they were arrested Oct. 24, "all hell broke loose.

"My son is dragged from the car. He is screaming and yelling. We are trying to figure out what is going on," Muhammad said.

The pair is also suspected of earlier shootings in Maryland, Alabama, Arizona, Georgia, Louisiana and Washington state.

Malvo's anticipated testimony may electrify a trial that so far has largely been devoid of drama: Muhammad was sentenced to death at his Virginia Beach trial in 2003 and faces at most a life sentence if convicted in Maryland. Much of the testimony at the Maryland trial, now beginning its fourth week, has been a carbon copy of the evidence introduced at Muhammad's first trial.

Muhammad is representing himself in the second trial — something he did briefly in the first trial — and that has added an element of unpredictability.