Lawyers for sniper suspect John Allen Muhammad appear ready to use a mental health defense to save their client from the death penalty if he is convicted, according to court papers unsealed yesterday.

The attorneys' official notice of whether they intend to use such a defense was sealed, but two motions filed by prosecutors indicate that the defense plans to use Muhammad's mental state as a mitigating factor if there is a sentencing phase.

In a motion filed Tuesday and released yesterday, prosecutors wrote that the defense "intends to present expert psychological testimony in mitigation." Prosecutors asked the court to provide them with a mental health expert to evaluate Muhammad.

Prosecutors said that Park Dietz, one of the country's most prominent forensic psychiatrists and experts on serial killers, has agreed to evaluate Muhammad. Dietz, who testified for the prosecution in the cases of Jeffrey Dahmer and John Hinckley Jr., earned his M.D., Ph.D. and master's in public health at the Johns Hopkins University. He is based in Newport Beach, Calif.

The court has paid for 100 hours of work by a defense team psychologist, including several interviews with Muhammad that lasted up to six hours each. Last month, the judge agreed to a defense request to transport Muhammad to a Prince William County hospital for medical testing and further evaluation.

In another motion released yesterday, prosecutors asked for the results of those tests and the reports of the defense team's psychologist.

Muhammad faces trial next month in the killing Oct. 9 of Dean H. Meyers at a gas station near Manassas, Va., one of 13 sniper shootings last fall that terrorized the region. His co-defendant, Lee Boyd Malvo, will first stand trial in Fairfax County, Va., in the killing Oct. 14 of FBI analyst Linda Franklin outside a Home Depot.

Legal experts said Muhammad's defense team had little choice but to put on a mental health expert at sentencing, even though it means the prosecution now has the opportunity to have its own expert examine the suspect.

"It's a very critical decision for the defense because ... there's always a risk when you have a prosecution examination of your client," said James Hingeley, the public defender in Charlottesville, Va. "It can cancel out some of the positive stuff you have."

But Abraham Dash, a professor at the University of Maryland Law School, said the defense has to provide the jury with some justification to sentence Muhammad to life in prison rather than death, if they convict him.

"If they [the jury] want to go the way of mercy, then the defense psychiatrist gives them a legal crutch to base their decision on," said Dash, a former federal prosecutor. "I really don't think a reasonably good defense lawyer has any choice."