Suspected sex attacker Peter Braunstein will likely use an insanity defense at trial - but it probably won't work because the Halloween assault was so sophisticated, experts said yesterday. Braunstein allegedly stalked his victim, set two small blazes and impersonated a firefighter to gain access to her Chelsea home, telltale signs that he was in command mentally, a former prosecutor said. "This would seem to be easy for a prosecutor to combat the traditional insanity defense," said Linda Fairstein, former head of the Manhattan district attorney's special victims unit. "He used a very clever way of entering her apartment, something that showed real intelligence." "He seems to have mapped out both his attack and his flight out of town," said Fairstein, now an author. "A prosecutor would seize on that to state that he knew what he was doing."

After weeks on the run, Braunstein attempted a spectacular suicide Friday by repeatedly stabbing himself when he was cornered by a University of Memphis cop. "Screaming, 'I am the man the world is looking for,' and then plunging a knife into his neck was a very public and very disturbed thing to do," said Susan Xenarios, director of the Crime Victims Treatment Center at St. Luke's Hospital. "But it may also have been very smart, because it sets up the insanity defense," she continued. "It makes him look crazy, but it may have been calculated."

Once Braunstein recovers, he'll be arraigned in his hospital bed or in a Memphis courtroom before a possible fight over his extradition to New York - a fight he would eventually lose, legal experts said. He will then be evaluated by a court-sanctioned psychiatrist who will determine whether Braunstein's mental well-being is sufficient for him to stand trial.

"Being 'crazy enough' to put a knife to your throat is not necessarily the legal definition of mental illness," said Arthur Aidala, a prominent city defense attorney. "Considering the circumstances of the attack, this will be a challenge for his side to prove." Insanity pleas are usually reserved for murder trials and are rare for sexual assaults, but Aidala believes that it would be a defense attorney's best option to combat the myriad charges - including sexual assault, kidnapping and arson - that could be tossed at the ex-journalist. "Even if he is found not responsible due to a mental illness or defect, it's not like he's getting right out to walk the street," Aidala said. "He could be released someday, but he'd have a long stay in a mental institution first."