OSHKOSH, WIS., NOV. 6 -- In a day of testimony so novel that the alleged sexual assault victim was alternately referred to as "she," "he" and "them," psychotherapists today described the complex mental history of a woman who has charged that she was violated by a man who took advantage of her multiple personality disorder by coaxing one naive and compliant personality into sex.

"Leona, Eleanor, Evan, Frank," recited Lori Warchol, a psychiatric social worker, listing for the prosecutor the names of a few of the woman's separate personalities that Warchol said introduced themselves to her in therapy last February. At the time, the young woman had been seeing Warchol for more than two years, and had complained of blackouts, mood swings and hearing voices conversing inside her head, Warchol said. But it was not until 10 months ago that the woman was diagnosed as a multiple personality, and Warchol testified that after that diagnosis she was able to contact the woman's personalities and come to know them by name.

"Eleanor is an older part -- her role or duty tends to be to try to keep control, and resolve conflict inside," Warchol said. "Franny is a more maternal part, and also does domestic duties and household chores. ... I believe Frank is more internal. ... He likes to do some reading. I think he perceives himself as a scholar."

The defendant, a married 29-year-old grocery worker named Mark Peterson, watched with apparent absorption as Warchol offered capsule descriptions of a few of what she said today are 46 personalities, or fragments of personalities, within the same woman. The 27-year-old woman, referred to here only as "S." to protect her privacy, met Peterson last June at a lake-shore park in Oshkosh. He has never denied having sex with her in his car two days later; in August Peterson was charged with felony sexual assault under a Wisconsin law that makes it a crime to have sex with a person who is mentally unable to monitor his or her own behavior.

To obtain a conviction, which could bring Peterson a sentence of up to 10 years in prison, the state must prove that Peterson knew in advance that the young woman was mentally ill. Much of today's testimony turned into a kind of one-day psychology lesson, with Warchol and two psychiatrists using vivid detail and finally an annotated slide show to illustrate the dividing of a human mind.

Lengthy articles were held up before the jury, and colored displays showed the results of studies that have reported different brain wave patterns among separate personalities within the same body. Each time defense attorney Edward Salzsieder took his turn to ask about this research, he wondered in his questioning how an untrained person might recognize such a syndrome -- if psychiatrists took so long to diagnose the woman in this case, Salzsieder asked, how could a new acquaintance be expected to understand what was happening in a woman he had just met?

"Might a stranger off the street not instantly recognize that, with a brief, limited exposure?" Salzsieder asked Warchol, as she described the characteristics that distinguished, for example, the naive and music-loving Jennifer from the quiet and masculine John.

"If you spend any amount of time with the personality, and talk with the personality," Warchol said, "they readily come out and are open with their multiplicity."

"But somebody would have to be knowledgeable to recognize that?" Salzsieder asked again.

"Not necessarily," Warchol said.

The young woman's downstairs neighbor, Ruth Reeves, also testified that the multiple personalities were easy to identify once they had made themselves known -- and that Reeves and the woman herself had both told Peterson about the mental disorder soon after Peterson first struck up a conversation with them during a lakeside fishing expedition last June.

"Franny addressed the issue on her own," Reeves said, explaining that in the course of the fishing trip the young woman changed in personality from Franny to John to another personality named Jamie. The Franny personality "explained that they were multiples," Reeves said, "and there were younger personalities and older personalities in the body."

Reeves said she joined in the conversation with Peterson, and that she wanted to impress upon him what she saw as the vulnerability of her upstairs neighbor -- that S. "was mentally handicapped," Reeves testified. "I explained to him that what was going on was true, that S. had personalities in her body that were vulnerable."

Prosecutor Joseph Paulus asked if Peterson responded. "He said, 'I see,' " Reeves said.