BOOK REVIEW : Prosecutor Beats Subject to Death : SEX CRIMES: Ten Years on the Front Lines, Prosecuting Rapists and Confronting Their Collaborators <i> by Alice Vachss</i> ; Random House $20; 304 pages

How could a book with the title “Sex Crimes” be boring? How could this particular author be boring?

Starting in 1982, Alice Vachss was an assistant district attorney in Queens County, N.Y., prosecuting rapists and child molesters. She became chief of the county’s Special Victims Bureau from 1985 until she was fired--for political reasons, she says--in 1991. She appeared on the cover of the June 27 Parade as well as in a 1989 piece profiling her and three other women under the headline “These May Be America’s Toughest Prosecutors.” She’s also, incidentally, the wife of Andrew Vachss, author of spectacularly violent novels that both dramatize and protest crimes against children.

This book’s initial 80-some pages, nevertheless, are inescapably tedious, suggesting the title, “Sex Crimes: The Prosecutor’s Resume.” And when Vachss finally gets to the cases she has tried or assisted in, touching on 17 and telling four in detail, she buries many of her stories in speechifying or repetitive overwriting (over and over the defendants are referred to as “subhumans”). Too often, Vachss takes the drama out of courtroom drama.

These stories, however, have a power that can’t be suppressed even when awkwardly told. Vachss prosecuted a man who had raped and sodomized his daughter from the time she was nine until she was 31. Once she turned 18, the man said, the acts, often committed at knife point, were “just incest between consenting adults.” Vachss tells about being suspicious of a psychiatrist who had become an advocate for the father. “I didn’t like how easily the psychiatrist had adopted his patient’s concept that this was just an affair. . . . It was that kind of thinking that had allowed the legislature to put incest in the same section of the penal law as adultery, and to designate it the lowest category of felony.”

Vachss argued for a vivacious Queens single mother named Daisy, who arrived home from work as a barmaid to find that her 14-year-old daughter had been raped by a machete-wielding man. The man turned on the mother and raped her as well. He was found guilty of attacking the daughter, yet acquitted of raping Daisy because, as the defense lawyer argued, “She doesn’t strike me as the kind of woman who would be particularly affected by these events.”

Vachss made powerful enemies when she went to the press in a fury over the case of John German, friend of members of Congress, director of the Flushing Boys Club, and pedophile. She was bent on exposing the judge whose idea of punishment for German was probation, followed by a speaking tour to educate the public.

She’s mad at judges, she’s mad at attorneys who defend rapists and she’s also mad at her fellow prosecutors. They want Good Victims; with a Good Victim you’re likely to win. “In New York City,” she writes, “Good Victims have jobs (like stockbroker or accountant) or impeccable status (like a policeman’s wife); are well-educated and articulate, and are, above all, presentable to a jury: attractive--but not too attractive, demure--but not pushovers. They should be upset--but in good taste--not so upset that they become hysterical.”

To ensure that their conviction rate will be high, prosecutors tend to decline cases “without incontrovertible proof.” “The trade-off,” she writes, “is that if cases are evaluated solely on the basis of likelihood of conviction, then the dangerousness of the offender . . . becomes secondary.” (On the other hand, when jurors send someone to jail they tend to feel better if they have incontrovertible proof.)

Despite these good points, Vachss is more often guilty of over-trying her case. Writing of serial rapist Emanuel Santana, she says, “His soul was smeared across years of crimes, stained in the lives of his victims.” It’s enough to hear that Santana waited in a car for a woman getting off work, slit her throat when she struggled, and drove around Manhattan as she began to bleed to death. He wanted to rape her, but complained later to the police that the sight of her blood turned him off.

The word shrill has gone way out of fashion, along with words like hysterical , which were overused to discredit arguments made by women. But one of the definitions of shrill applies precisely here--”Betraying some strong emotion or attitude in an exaggerated amount, as antagonism or defensiveness.”

“Of course my book is antagonistic and defensive,” Vachss might say. “These crimes are outrages, and bad judges and prosecutors and juries let dangerous criminals back on the streets. What do you want, a fun read?”

Vachss wanted to write a book that would make us feel as strongly as she does. But she needed to tell her stories in a way that makes us listen. Given Vachss’ high-pitched writing, this isn’t usually what happens. And so in the end, “Sex Crimes” quickly gets monotonous and becomes, finally, a trial to read.