ROCKVILLE, Md. – Washington area sniper Lee Boyd Malvo is negotiating a plea bargain in which he would testify against his former mentor John Allen Muhammad, a person familiar with the case said yesterday.

Negotiations between prosecutors and Malvo’s attorneys have not been finalized, but Malvo is prepared to testify about the shootings and his relationship with Muhammad, the source said.

The source, who confirmed the report by WTOP radio in Washington, requested anonymity because the deal was not complete.

Under the terms being considered, the source said Malvo would plead guilty in connection with the six shooting deaths in Montgomery County, where the spree began and ended.

He would be sentenced to life in prison, the maximum sentence for a homicide committed by a juvenile. Malvo, now 21, was 17 at the time of the shootings and is already serving a life sentence in Virginia.

If Malvo accepts the agreement, it would mark the first time he testifies against his fellow defendant. Malvo appeared briefly at a pretrial hearing before Muhammad’s Virginia trial, but didn’t testify.

J. Wyndal Gordon, one of Muhammad’s three standby attorneys, said he’s not surprised to hear negotiations were in progress since Malvo has been listed as a potential witness by both the prosecution and the defense. Mr. Gordon said Malvo would have credibility problems.

“He’s not going to be the star witness for the prosecution,” Mr. Gordon said.