A forensic psychologist struggles to prove that the killer of two old women was insane, in a fact-based case courtesy of Kennedy (Welcome to the End of the World: Prophecy, Rage and the New Age, p. 854, etc.) and first-novelist Sultan. Dull-witted delivery boy Jimmy Wier must have been in the grip of some powerful compulsion when he murdered Lila Mooney, 83, and her friend Constance Bennet, 90, then raped and mutilated them and ran off with a stolen box of Devil Dogs and an African violet he was captured trying to bury. But does that compulsion fit the legal definition of insanity? Politically-minded Dixon (S.C.) D.A. Donny Royal, baying for the death sentence, couldn't care less, and he's willing to hire hack diagnostician Harry Falcone to say that Jimmy, quiet and well-behaved now that his medications have been properly adjusted, is as sane as you or me. So Jimmy's fate is up to defense consultant Portia McTeague, a forensic psychologist who's already seen more horrors than she ever wanted and whose abusive childhood is an uncomfortable parallel to Jimmy's own. The early scenes between Portia and Jimmy crackle with authenticity as you feel how hard it is for her to reach this agonized, profoundly alienated man on any level, and they lend an edgy sense of difficulty to her job. But once Portia and flirtatious p.i. Alan Simpson start to uncover evidence about Jimmy's monstrous upbringing and tease out a diagnosis practically unheard of except among ``quacks and movie- of-the-week psychological experts,'' everything suddenly gets much too easy. The defense discovers evidence-tampering; the prosecution's own expert tells the D.A. that ``Wier's sick''; and a therapeutic quickie with obliging Alan suggests that Portia may be ready to put her own troubled past behind her. Realistically rough in the early going, then, but hampered by a fatal lack of invention.