A Cop Torn Between the Law and Justice : CHAIN OF EVIDENCE by Ridley Pearson; Hyperion; $22.95, 348 pages

Many Americans are outraged with a justice system that releases psychotic sex offenders who end up repeating their crimes. But few get the chance to “correct” judicial error and mete out justice, as Walter Zeller does in Ridley Pearson’s novel “Chain of Evidence.” A retired forensic specialist from the Hartford, Conn., police department, Zeller has seen enough sex crimes in his day, and decides to put a stop to them.

Caught between revulsion for the crimes of Zeller’s victims, and his duty to protect the law he suspects Zeller has lost sight of, Lt. Joe Dartelli doggedly pursues the truth.

“Chain of Evidence” marks Dartelli’s first appearance, but presumably not the last. Pearson, the first American to win the Raymond Chandler Fulbright at Oxford University, has published eight other novels, four featuring another male police detective with a female sidekick.

The formula works here, too. Dartelli is a classically morose, honest cop whose character is partially explained by the psychological scars he bears from a nightmarish childhood. Among other horrors, he found sanctuary from his abusive alcoholic mother in the barrel of an automatic clothes dryer.

Dartelli is estranged from Ginny, a brilliant hacker who has been caught more than once in computer breaking and entering. She simply cannot, it seems, go straight and Dartelli cannot tolerate marriage to a law-breaker.

Pearson almost immediately complicates Dartelli’s emotional life by sending him into the arms, and bed, of another police officer, Lt. Abigail Lang, a not-quite-divorced mother of two who has manipulated the police hierarchy to create a separate, one-woman detail for sex crimes.

Lang bends departmental rules for Dartelli, all the while urging him to follow his intuition, no matter where it takes him.

It takes him mostly to seedy, dangerous, inner-city Hartford. There are also excursions to wealthy, woodsy suburban Connecticut as well as to Hartford’s insurance megaliths and to Trinity College.

Pearson begins his tale in August as Dartelli responds to a radio bulletin that another “flyer” (police lingo for suicides who exit upper-story windows) is down in front of the not-very-elegant downtown Granada Hotel. It’s an open-and-shut case, except that the body fell head first and a witness saw him “dive.” Dartelli knows that suicides always jump. Using a computer reconstruction of the incident, Dartelli proves that the victim was pushed.

The incident reminds him of a similar, earlier episode he had written off as suicide. That victim, like the new corpse, had a history of sexual offenses. Dartelli proceeds to expose a series of apparent “suicides” as skillfully disguised murders of sex offenders.

Dartelli’s suspicion that the killer is a cop, and probably Zeller, is never secret. The real meat of this thriller lies in Zeller’s motive: More than simple revenge, it involves the high-stakes world of genetic engineering.

The title “Chain of Evidence” has a double meaning. A chain of evidence is the name given to the tangible body of clues turned up by the forensic team. But it is also the double helix of the DNA molecule, illustrated on the book jacket with a body caught in the familiar spiral.

Forensic sleuthing is not enough for Pearson, who goes on to introduce hard science into his plots. “Chain of Evidence” suggests that sex offenders can be treated with gene therapy. If such a treatment were possible, would it be any more viable than castration, hormonal treatments or neurosurgery--all medical efforts that “work” insofar as they prevent the criminal from repeating the crime, but are illegal because they constitute “cruel and unusual punishments”? Could the courts sentence sexual abusers to gene therapy, even though they cannot, under current laws, require mothers who abuse or kill their children to have tubal ligations?

These questions may be heavy for a simple thriller, but since the author raises them, they cannot be completely dismissed.

The ethics of genetic engineering notwithstanding, most readers will agree that the nasty fellows whose corpses Dartelli finds deserve their fate. Some readers may wonder, as I did, if Dartelli made the right choice in women. But as such choices are anything but permanent in the milieu of detective fiction, it is possible we will meet Dartelli in another Hartford adventure with another set of romantic options.