Scott Peterson shouldn't profit by selling the story of wife Laci's murder, her mom said yesterday in a lawsuit asking that her family get any money earned from book, movie or other deals Scott makes.

The lawsuit — filed by Sharon Rocha's (search) family by lawyer Adam J. Stewart — asks a court to create an involuntary trust that would intercept Scott Peterson's (search) profits from the story.

Scott, a fertilizer salesman, has pleaded not guilty to charges of murdering his pregnant wife on Christmas Eve and dumping her body in San Francisco Bay (search).

The Rocha family's lawsuit appears to be without legal merit, said a constitutional-law expert —who added that Laci's relatives might do better if they filed an unlawful-death suit.

"They can't do it this way," said Erwin Chemerinsky, a law professor at the University of Southern California.

New York's law barring criminals from profiting from by their stories — called the "Son of Sam" law (search) after serial killer David Berkowitz (search) — was declared unconstitutional by the U.S. Supreme Court in 1991.

California's Supreme Court made a similar decision a year ago in a case involving the kidnapping of Frank Sinatra Jr.

In both cases, the courts said the laws infringed on suspects' free-speech rights — and Chemerinsky said Laci's parents will encounter the same legal problems.

Peterson's criminal defense lawyer, Mark Geragos (search), said he hasn't yet seen the lawsuit and couldn't discuss it or predict whether he'd be hired to defend against it.

Stewart, the Rochas' attorney, could not be reached for comment.