Yellow legal pad in hand, convicted killer John Allen Muhammad pointedly questions a Virginia police officer who has identified Muhammad as the man he stopped behind the wheel of a Chevrolet Caprice, and released, during a police dragnet near an Oct. 9, 2002, sniper-style killing in Manassas, Va.

Muhammad has seized on a small disparity between Officer Steven Bailey's descriptions from the witness stand about the age of the driver - between age 40 and 45 - and his written Nov. 8, 2002, statement that the driver was between 45 and 50.

"I did not remember the words, word by word," Bailey says after reading his old statement, sounding peeved. Muhammad, who now is 45, asks him about it repeatedly.

"I just told you, 45 to 50," Bailey retorts.

Outside the courtroom, Bailey characterizes Muhammad as "fishing. He doesn't have a clue. He's stuck."

The scene of Muhammad - on death row in Virginia for one of the 2002 Washington-area sniper shootings - cross-examining police officers, other witnesses and even a survivor has been one of the more bizarre aspects of his six-count murder trial in Montgomery County. A judge allowed Muhammad to represent himself over the objections of his former lawyers, whom he fired after they argued that he was mentally ill. Three standby lawyers are assisting him.

Muhammad's questioning from behind the defense table - he is barred for security reasons from approaching the bench - has added drama to the proceedings. But several veteran lawyers familiar with his case say it is unlikely that Muhammad's apparent legal strategy - finding small discrepancies, getting prosecution witnesses to acknowledge that they didn't see the shooters - will sow the seed of doubt in jurors.

"He is asking those questions because that is all he can ask. But it is meaningless. The case against John Muhammad is one of the tightest circumstantial cases I have ever seen," said Richmond, Va., lawyer Steven D. Benjamin, a board member of the National Association of Criminal Defense Lawyers.

Muhammad was convicted of murder in Virginia in 2003 in the fatal sniper shooting of Dean H. Meyers at a Manassas gas station. The verdict is on appeal. Authorities say he and Lee Boyd Malvo were responsible for 13 sniper shootings, 10 fatal, in the Washington area in the fall of 2002.

Malvo - with whom Muhammad was arrested Oct. 24, 2002, at an Interstate 70 rest area in a dark-blue Chevrolet Caprice that authorities say served as a mobile sniper's lair - is serving life prison sentences in Virginia for three sniper shootings there, two fatal. Malvo might testify against Muhammad as part of a plea agreement in the six Montgomery County killings. That could bring Malvo face to face with the man Muhammad calls his "son."

In the past week, Muhammad has asked prosecution witnesses - including a doctor involved in autopsies of some of the victims - if they had "personal knowledge" of who committed the killings or if they saw who fired the shots. None did.

Muhammad looked satisfied when an auto dealership worker testified that he believed the blast he heard Oct. 3, 2002, that killed James "Sonny" Buchanan was from a shotgun, not a rifle. But that is another irrelevant distinction, lawyers say. Jurors will hear expert testimony that in the Virginia trials of Muhammad, Malvo tied that and other shootings to the .223-caliber Bushmaster rifle that police say they pulled from Muhammad's car.

"In the long run, is this going to advance the ball for him? No," said Michael Greenberger, law professor at the University of Maryland and director of the university' s Center for Health and Homeland Security. Chipping away at prosecution witnesses can be part of a defense strategy to show that the state has failed to prove its case, he said, but "the question is whether he can bring it home when this forensic evidence comes in."

That evidence, unveiled in the Virginia trial, will include the Caprice, the rifle, and DNA and fingerprints that experts tied to the October 2002 sniper shootings. Muhammad will have no expert witnesses to counter them.

Jose F. Anderson, a University of Baltimore law professor who formerly was with the public defender's office, said many defendants "think that discrediting a story alone will build a defense." They also believe that each tiny point has a huge impact on a jury, when "in truth, it doesn't," he said.

"On the other side of it, he is using what he has," Anderson said. "He is trying to impeach the general credibility of the evidence, hoping this will bear fruit."

In the cavernous Rockville courtroom, Muhammad assumes the role of a lawyer. Attired in clothes from his two male standby lawyers, down to French-cuffed shirts, he leans over collegially to whisper to the lawyers just the way it's shown on television, and has much - though not all - of the legal terminology correct. His questions have baffled some witnesses. He always has at least one legal adviser on his right, less noticeable than the sheriff's department tactical team around him. Because he cannot leave the defense table, he tells the standby lawyers what items of evidence to bring to witnesses, the clerk, the judge, the prosecutors.

"You can look good and you can speak well - you can have great courtroom presence," Anderson said. "But if you are asking the wrong questions, those things are not going to help you."

Still, he added, another factor might be at work: His future grim, Muhammad might want to be in charge and aggravate prosecutors and the judicial system as much as he can.