The witness stand can be a dangerous place for a defendant.

Cross-examination by the prosecutor can be brutal. Objections from defense attorneys can look like an attempt to hide something. And the way the defendant looks and acts on the stand can prove more powerful than what he or she has to say.

"Even innocent defendants can look guilty on the witness stand," said Loyola Law School professor Laurie Levenson.

It is a chance Scott Peterson's (search) attorneys probably won't take.

In nearly 19 weeks of trial on charges of killing his wife, Laci, and the fetus she carried, Peterson has already become his own worst witness. Through wiretapped phone calls and videotapes played in court, the jury has seen and heard him carrying on an affair and lying repeatedly to girlfriend Amber Frey (search), to reporters, to police, and to friends and relatives.

"Peterson is a compulsive liar," Levenson said. "If he takes the witness stand, the prosecution has such an easy way to undermine his credibility. If he's willing to lie about small things to Amber Frey and to family members, imagine what he would lie about if his life were on the line."

Defense lawyers have tried to explain away his behavior as that of a man on the run from a crush of media — not from police, as prosecutors claim. When the defense begins presenting its case next week, his attorneys may point to another reason for his seemingly odd and evasive actions — death threats that had Peterson fearing for his life.

That could help him explain why, for example, he had dyed his hair blond and had left his hometown of Modesto by the time he was arrested.

But the risks involved in taking the stand might still be too high.

"I would be worried that Peterson would come off smirky, too clever or arrogant," said Michael Mello, a Vermont Law School professor who served as one of serial killer Ted Bundy's (search) attorneys on appeal and wrote a book about Unabomber Ted Kaczynski (search).

"The risk is confirming the jury's suspicion that this guy ... really is as much a slime as he appears to be," Mello added. "My mother used to have a saying: `It's always better for people to wonder why you didn't open your mouth than to have people wonder why you did."'

Many legal experts agree that defense attorney Mark Geragos (search) has done a good job at presenting Peterson's side through the cross-examination of prosecution witnesses and raising at least some reasonable doubt that Peterson is the killer.

Putting him on the stand "would really be a huge mistake in a case like this ... because it would throw away all of the benefits of being able to say they simply haven't proved their case," said Peter Kean, a professor at Golden Gate Law School.

Peterson, 31, could get the death penalty if convicted. The bodies of Laci Peterson (search) and her fetus washed up along San Francisco Bay, about two miles from where Scott Peterson claims he was fishing alone on Christmas Eve 2002, the day his wife disappeared. Prosecutors say he killed her so that he could carry on with Ms. Frey.

Both sides are bound by a gag order, and Peterson's lawyers have not said what they are going do. But his attorneys did at least consider putting him on the stand. They even took time early on to prepare him, in case they felt a win slipping away.

Martha Stewart (search) did not testify before she was convicted of lying about a stock sale. O.J. Simpson (search) also did not take the stand, and was acquitted of murdering his ex-wife and her friend. Experts say he made the right choice, given his record of violence against his wife. After he was forced by law to take the stand in a wrongful-death civil case, he was held liable for the slayings and ordered to pay $33.5 million.

"I was there and when O.J. took the witness stand, he looked like a killer, he would clench his jaw and make a fist," Levenson said.

But there is also a risk when defendants do not take the stand.

Jurors are instructed not to hold it against a defendant if he does not testify in his own defense. "But it's human nature to wonder why he's not taking the stand," Mello said, "especially in a case like this where the crime is so horrible. You can't change human nature with a jury instruction."