Imagine you're a defense attorney trying a complex free-speech case with multiple defendants. Before the trial a police detective says to you, "They'll all be convicted. A will get one year, B two years, C five and your client seven." And suppose that after a long and contentious trial, those are precisely the sentences the judge hands down. Would you conclude that: 1. this is a remarkable coincidence; 2. the detective is psychic; 3. the trial was a charade? Before answering, add one more fact: the trial took place in the Soviet Union.

If you chose 1 or 2, "Final Judgment," Dina Kaminskaya's open-and-shut case against the Soviet legal system, will set you straight. And even if you did choose 3, the book will expose you to dimensions of travesty you may not have anticipated.

A defense attorney for 37 years, until she and her husband were evicted from the Soviet Union in 1977, Kaminskaya had just such an "uncanny" experience while representing Yurii Galanskov, a dissident poet. Because the outcome was predetermined by the KGB, Kaminskaya calls the trial "a cruel farce." And in fact many of her trials had an air of theatrical foolishness about them. Often the gallery was crammed with hand-picked righteous citizens--the KGB's "Rent-a-Crowd"--who jeered and interrupted the proceedings like groundlings at a melodrama.

Some of the judges were shamelessly hostile to the defendants; others were ludicrously ignorant. The tallest dunce cap goes to a noodle named Pisarenko, who presided over the trial of several Tartar nationalists. The subject comes around to the 1968 Soviet invasion of Czechoslovakia, which Ilya Gabay, Kaminskaya's client, publicly condemned. Judge Pisarenko wonders how Gabay possibly can doubt the authority of the Soviet newspapers, which explained it all: the Czech people summoned the Soviets to rescue them from bourgeois freedoms. With some coaching from Kaminskaya, Gabay brings up the notorious articles published in 1953 which exposed a doctors' plot to kill Soviet leaders. Three years later the same papers admitted the doctors' plot as a canard.

The riposte leaves Pisarenko unfazed. " 'But, Gabay' ", he replies, " 'you're contradicting yourself. You say yourself that the Soviet newspapers later published a denial. Correct? And was there a denial about Czechoslovakia? When they do print a denial, then you can say so.' " This might be an uproarious exchange in a comedy by Gogol or the Czech satirist Jaroslav Hasek ("The Good Soldier Schweik"), but as an incident in an actual trial, it evokes nervous laughter.

As depicted by Kaminskaya, Soviet law is rife with nervousness: every gesture toward fairness is checked by anxious second thoughts. The Soviet Constitution, for instance, includes an edifying bill of rights, which Kaminskaya and her colleagues never lost an opportunity to cite. How, then, can judges get away with ejecting witnesses, suppressing evidence and jailing people just for raising banners? The catch is that the Soviet Constitution is not meta-law like the American. There is no method of declaring a Soviet statute unconstitutional, which means that every latest law supersedes guarantees in the constitution.

In the course of recounting her greatest cases, Kaminskaya sketches the outlines of Soviet criminal practice. The function of defense attorney is anomalous in the Soviet Union, where the state makes no errors, but is tolerated for the sake of the regime's image abroad. Although her branch of the profession ranks low in prestige, it is unusually independent: "Unlike the overwhelming majority of all other working citizens of the Soviet Union . . . defense advocates are not state employes and receive no salary or other monetary reward from the state." And though prescribed fees are low, a defense attorney can do quite well by pocketing mixt, an extra, illegal fee that customarily is offered (but never accepted by Kaminskaya). Soviet attorneys may not ethically defend a guilty client who pleads not guilty, but if the client admits his guilt, the attorney can represent him by asking the judge (there is no trial by jury) for mercy.

It's a stern system compared to the Anglo-American, but it might yield an approximation of justice if everybody played by the rules. Kaminskaya always did. Her grand passion as a lawyer was not for the Platonic form of justice or even for her clients' rights, but for her profession and its potential to make the system work. In nonpolitical trials she frequently succeeded, in one case unmasking an overly ambitious prosecutor who framed two teen-age boys to get a murder conviction.

She fared less well when defending dissidents and demonstrators, but at least she compelled the authorities to ponder their ham-handed manipulations. She had to leave the country not because of her political views, which she kept to herself, but because she insisted on maintaining professional standards.

How she can write about all this with restraint and even generosity, I don't know. (She compliments the KGB on the last page for its "kind help" in arranging her relatively smooth emigration.) But her equanimity enhances the force of her observations. This absorbing and instructive book is conclusive evidence that Kaminskaya has mastered another profession--writing.