Plea of Insanity By Jilliane Hoffman (Vanguard Press. $25.95)

If you like legal thrillers, make yourself a note to read "Plea of Insanity" by Jilliane Hoffman. It won't be out until next month, but it's worth waiting and looking for. The protagonist is Julia Vacanti, a young, inexperienced prosecutor assigned as second chair in a high-profile murder in Coral Gables. The wife and three children of David Marquette, a successful Miami surgeon, were brutally slaughtered while he sustained only minor wounds. He is charged and brought to trial for their murders. If convicted, he faces the death penalty.

Dr. Marquette's experienced and clever defense attorney mounts an insanity defense, claiming that paranoid delusions resulting from schizophrenia caused this perfect husband and father to snap and murder his family. Ms. Vacanti and Rick Bellido, her lover and brilliant, ambitious co-counsel, suspect that behind Dr. Marquette's insanity plea lurks a deliberate, cold-blooded murderer.

Of equal interest in this book is the subplot wherein Ms. Vacanti is forced to explore her own past, which involves a similar tragedy. Ms. Vacanti, who for years has told everyone that her mother and father died in an automobile accident, unwillingly confronts that lie and acknowledges to herself that her parents were murdered by a family member.

She is torn and tormented by conflicting memories of her past and, as the book progresses, and she deals with the gradually returning memories of her childhood, she finds herself doubting her earlier conviction that

Marquette is sane.

As the case comes to trial, Mr. Bellido, who's being touted as the next district attorney, wants and needs a victory in this case and he's determined to get it at any cost. Ms. Vacanti is under increasing stress that she now must deal with to save her sanity. The question remains almost until the last page: Is Dr. Marquette playing the system or genuinely insane?

Ms. Hoffman is a skilled writer. Her plot is full of unexpected twists; however, at no time, does the plot overshadow her engaging characters, including the hunky cop who comes to care deeply for Vacanti and a circle of interesting fringe folks. This author also provides an intriguing look behind the closed doors of the Miami-Dade circuit court system where prosecutors are As, Bs or Cs depending on whether they routinely handle misdemeanors or felonies. Ms. Hoffman also knows Miami — and, of course, she should. She began her professional career as an assistant state attorney prosecuting felonies in Florida from 1992 to 1996.