For all the lurid details and the almost voyeuristic interest that surrounds it, the trial that begins today for John Wayne Bobbitt will be much like any other case of marital sexual assault.

And that means it will be tough to win a conviction, legal scholars say.

Bobbitt's wife, Lorena, has accused him of raping and assaulting her the night she made headlines by cutting off his penis with a kitchen knife.

The 26-year-old ex-Marine has denied that he attacked his wife.

"It's going to come down to who you believe," said Paul B. Ebert, Prince William County commonwealth's attorney. "It's not easy to prove a case when it's one person's word against another's."

Still, as much of the world knows, the Bobbitts' situation is far from usual. John's trial is something of a scene-setter for the trial later this month in which Lorena will be defendant, not victim. The 24-year-old Manassas woman is charged with malicious wounding for severing her husband's penis in the early morning hours of June 23. She says the undeniably gruesome act was provoked not only by an attack that night but also by years of abuse. The Bobbitts face 20 years in prison each if convicted of their respective crimes.

"There are two different stories that can be told, both of them consistent with the severed penis," said Pamela Karlan, a law professor at the University of Virginia. "A lot of what the jury decides depends on which of the two stories they believe."

Virginia's spousal rape law, under which John Bobbitt is being tried, took effect seven years ago and has been used only sporadically. According to legal scholars, winning a conviction on such a charge is often difficult because some juries won't accept that sexual consent could be absent within marriage. "For years and years, spousal rape was an oxymoron," said University of Virginia law professor Daniel Ortiz.

The Bobbitt case is especially challenging for Ebert because of the sensational act that followed the alleged assault. The prosecutor will try to use that act as evidence of John Bobbitt's continuing abuse of his wife. According to statements Ebert has made in several preliminary hearings, he will try to convince the jury that something horrible must have happened to drive Lorena Bobbitt to commit such a heinous act.

But Ebert says that discussing the severed penis could backfire, because jurors may decide that John Bobbitt has already paid for any crime against his wife.

As for the defense, lawyer Greg Murphy will argue that Lorena Bobbitt falsely accused her husband of rape to justify her crime. He could try to introduce evidence -- including Lorena's alleged embezzlement from a manicure salon where she works -- that suggests she is dishonest. She was never charged with a crime, and she agreed to return the money to her employer.

Murphy is expected to describe Lorena Bobbitt as an abusive and jealous wife who went over the edge when her husband told her that he intended to divorce her. "The story of their relationship has not been told," he said last week, "and I assure you that parts of it will be told."

Although more than 30 witnesses have been subpoenaed, both sides agree that the case will be won or lost on the testimony of John and Lorena Bobbitt.

Murphy, for example, is hoping that a jury will judge Lorena Bobbitt as he did when she recently appeared on ABC's "20/20." He described her as a woman who cried at all the correct times, and he derided her conduct as obviously rehearsed and insincere.

"I'm sure you'll see tears in court," Murphy predicted.

But John Bobbitt carries his own liabilities, Murphy conceded. James Sehn, one of the two doctors who reattached Bobbitt's penis, has called him "a monosyllabic type of person," someone not apt to impress a jury.

Murphy said his client has "attention deficit disorder," which often causes him to skip from subject to subject in mid-sentence.

"It took me a couple of weeks to be able to understand him," Murphy said. "He tends to mumble. But I've been working with him a lot on enunciating."

Picking 13 jurors, including an alternate, could be a challenge, given the extensive pretrial publicity. The judge said he will increase the potential jury pool from 24 to 36 people. He refused an early request to move the trial, but he said he would reconsider if seating a jury proves difficult.

Ebert has no illusions that he'll find people who haven't heard about this case. His challenge, he said, will be finding people who can remain open-minded despite the publicity. Murphy said he will be looking for jurors who admit to some biases. "I tend to think if you admit your biases, you're more likely to be open-minded," he said.

Yet both lawyers believe the case has been almost overwhelmed by the media attention. "For some," Ebert said, "the sensationalism is all that matters. The interest of justice is secondary, if not nonexistent."