OSHKOSH, WIS., DEC. 17 -- Saying the defense team should have pursued its request to psychiatrically examine the victim, a judge today ordered a new trial for a man convicted last month of sexually assaulting "Sarah," a woman who claimed to have at least 46 separate personalities.

Defendant Mark Peterson, an unemployed supermarket worker who faces a sentence of up to 10 years imprisonment, might now go free. Winnebago County Prosecutor Joseph Paulus said he may decide at a hearing later this week to drop the case entirely for fear that another trial would aggravate the victim's fragile mental condition.

Circuit Judge Robert Hawley said the new trial was necessary because Peterson's attorney, Edward Salzsieder, did not adequately follow up on his pretrial motion to have a defense psychiatrist examine the victim.

Sarah's fragmented testimony -- delivered in the voices of several of her 46 "personality states" -- led to Peterson's conviction last month. A jury decided Peterson, 29, seduced the 27-year-old woman in his car by summoning forth one of her personalities -- a naive and pliable character named Jennifer -- and manipulating her into agreeing to sex.

Convicted under a state law that protects the mentally ill from assault, Peterson was to be sentenced next month.

At the time of the conviction, legal and mental health experts hailed the decision as a victory for the rights of the mentally ill. But revelations that emerged after the sensational week-long trial, including information about Sarah's alleged romantic relationship with a witness, cast doubt on the verdict.

Multiple-personality disorder is a relatively rare condition where the victim creates characters that serve to block out the pain of earlier traumatic experiences. The alternate selves often display amazing talents and erratic behavior patterns of which the host personality is ignorant.

Sarah appeared with her attorney at a court hearing yesterday seeking to keep her medical records private. The records are being sought by a local newspaper.

Vince Biskupic, deputy district attorney for Winnebago County, confirmed today his office might drop the case simply to protect the victim.

"The initial goal of the prosecution was to focus attention on the rights of the mentally ill in society," he said, "and we don't want to compromise that goal by forcing a victim through a second trial when it could be a detriment to her."