Updated

A judge blocked John Allen Muhammad from presenting some of his defense evidence Thursday in the Washington-area sniper shootings, preventing him from questioning a police detective who Muhammad claims prodded his young accomplice to confess.

Muhammad, who is defending himself against murder charges in six Maryland sniper killings in October 2002, called witnesses who saw other suspicious vehicles at shooting scenes. He also introduced a search warrant from a Virginia home where investigators found more than 20 guns and bullets similar to those used in the shootings.

But Muhammad was repeatedly cut short by prosecutors and Judge James Ryan as he tried to question witnesses that included a Secret Service handwriting expert and a Virginia investigator. Ryan said Muhammad was not asking proper questions and didn't introduce evidence correctly.

Ryan quashed Muhammad's subpoena for Fairfax County, Va., Detective June Boyle, who questioned his teenage companion, Lee Boyd Malvo, after the two were arrested Oct. 24, 2002. Malvo testified against Muhammad earlier this week.

Muhammad began his defense late Wednesday, presenting several witnesses who said they saw other suspicious vehicles or people near crime scenes. On Thursday, two more people said they made similar police reports.

One of them, Heidi Mansen, saw the shooting of Pascal Charlot on Oct. 3, 2002, as she was stopped at a traffic light in Washington, D.C. She saw a red car stopped next to her drive away quickly and followed it, dialing 911 to report the license plate.

Mansen shifted uncomfortably as Muhammad questioned her, and said afterward that it was "scary" to face him. She realized that Muhammad wanted to use her to cast doubt on his involvement, but she wasn't convinced.

"I'm just one of many people who saw something and didn't see the reality of it," she said. "He's guilty."

Both Muhammad, 45, and Malvo, 21, already have been convicted of slayings in Virginia. Malvo is serving a life term in prison while Muhammad was sentenced to death. The second trial in Maryland has been billed as insurance if the Virginia verdict against Muhammad was ever overturned.

Malvo agreed to plead guilty to the same six Maryland murders this week and gave a detailed inside account of the planning and execution shootings. He said Muhammad — who he had once considered a father figure — devised the scheme to terrorize the region, and planned even more killings.

Muhammad claimed he and Malvo were simply driving around the Washington area looking for the children Muhammad had lost in a custody battle. He said in his opening statement that he would prove himself and Malvo innocent.

But during their three-week case, Montgomery County prosecutors presented a wealth of evidence against Muhammad. Ballistics experts testified that the Bushmaster rifle found in Muhammad's car when he and Malvo were arrested was used in the shootings. Malvo's DNA was found at crime scenes, and witnesses saw their Chevrolet Caprice and Muhammad near several shootings.

Malvo told Boyle that he was the triggerman in all 13 sniper shootings, but testified this week that he lied to protect Muhammad and said Muhammad was the triggerman in 10 shootings. When prosecutors objected to Muhammad's plans to call Boyle, he claimed Boyle fed sniper details to Malvo when he confessed.

Muhammad and Malvo also are suspected of earlier shootings in Maryland, Alabama, Arizona, Georgia, Louisiana and Washington state.