After deliberating for three hours, a jury of six men and six women voted earlier this month to acquit Vladislav Kozachenko of the February 2004 murders of a 25-year-old woman who ran a prostitution ring in this southern Russian city and her 39-year-old lover.

Kozachenko thanked the jury from behind the bars of the courtroom cage where he sat during the three-week proceeding. But the relief visible on his face must have been tempered by the fact that twice before he had heard different juries pronounce him not guilty of the same crime. And twice before, prosecutors had refused to accept the verdict and brought him back to trial.

"I hope it's third time lucky for me," Kozachenko, 36, said after his release. "Maybe they will let me go now and look for the real murderer."

That remains to be seen. Prosecutors immediately vowed to appeal the verdict to the Russian Supreme Court and secure a new trial. "We are convinced the murder was committed by him," said Natalia Kalikanova, the lead prosecutor in Kozachenko's third trial. "He's guilty. We cannot leave an unlawful verdict in force."

Twelve years after its introduction as a landmark legal reform in a country just emerging from communism, the jury system remains the object of suspicion, even contempt, among prosecutors and some judges in Russia. "I would abolish it," Kalikanova said flatly.

Juries were introduced as part of an almost complete overhaul of the former Soviet legal system in the 1990s. On paper, it drew widespread admiration from government leaders. But scholars and human rights activists charge that the system still reflects the values of the old communist-era courts, in which a presumption of guilt prevailed. To them, the jury system's failure to take root and recent proposals to scale it back are part of a broader rollback of democratic practices and institutions in President Vladimir Putin's Russia.

Under Russian law, double jeopardy is not prohibited. Prosecutors, as well as defendants, can appeal verdicts, and almost all jury acquittals are appealed. In the past five years, between 25 percent and 50 percent of not-guilty verdicts returned by juries were reversed by the country's Supreme Court, according to annual court statistics and analyses by Russian legal scholars.

"Nobody thought so many verdicts would be overturned," said Sergei Nasonov, a professor of criminal law at the Moscow State Law Academy who has written a book on jury trials in Russia. "The reasons for overturning jury verdicts were supposed to be very limited, but the Supreme Court has interpreted the law very broadly. A jury verdict is hardly ever the final word."

Still, juries remain a significant check on the power of the state. Prosecutors were long accustomed to getting automatic guilty verdicts when they decided to go forward with a trial. Year after year, only between 1 percent and 2 percent of defendants are acquitted in bench trials in Russia, statistics show, compared with about 15 percent in jury trials.

In Krasnodar, there have been years when not a single person was acquitted by a judge, but nearly a third of defendants in jury trials were acquitted, according to regional court statistics.

Often, jury verdicts are overturned on highly technical grounds.

Kozachenko's first not-guilty verdict, in September 2004, was reversed because the judge failed to officially notify a relative of one of the victims of his right to make a final statement to the jury, which voted 11 to 1 to acquit. In Russia, a jury verdict is decided by a majority vote of the panel.

The second acquittal, in April, was overturned because of errors in the judge's written charge to the jury, which had been unanimous in finding Kozachenko not guilty.

After the 8 to 4 vote in favor of the defendant this month, Kalikanova, the lead prosecutor, said she discovered that some jurors on the panel "concealed certain information about themselves, criminal records and previous service in the police." The post-trial discovery of such information is frequently invoked in appeals to the Supreme Court.

"When a not-guilty verdict is passed, the prosecutors begin to dig around," said Judge Nina Stus of the Krasnodar regional court, who has presided over more than 100 jury trials. "It's a card prosecutors keep up their sleeve in case there is a not-guilty verdict."

Some of her colleagues on the bench "categorically refuse to participate in jury trials" because they are "unpredictable," Stus said.

At the same time, pressure is mounting to limit those eligible for a jury trial. The Supreme Court, exercising its prerogative to propose legislation, recently called for a law restricting jury trials to murder cases.

According to Nasonov, the criminal law professor, the Supreme Court is already using its rulings to steadily narrow jurors' ability to assess evidence in an effort to make juries more "manageable."

Nasonov argues that enforcement of the principles of presumption of innocence and proof beyond a reasonable doubt are key to restoring Russians' faith in their legal system. The system is now widely seen as entirely predictable -- a railroad to prison even when hard evidence is clearly lacking.

Mara Polyakova, a former prosecutor and chairwoman of the Independent Council of Legal Experts, said she recalled prosecutors showing up on the first day of a trial without having read the case material, because, she said, they were so confident the court would simply accede to their demand for a guilty verdict.

"Prosecutors are simply not used to the fact that decisions are being passed which they don't control," said Polyakova, who worked in a prosecutor's office for 27 years. "In front of a jury, they have to work harder."

The jury system was introduced in Russia in 1864 but abolished by the Bolsheviks in 1922, even though they had almost always opted for jury trials when they were charged with sedition before the 1917 revolution.

In 1993, two years after the breakup of the Soviet Union, jury trials were reintroduced in nine of Russia's 89 regions, including Krasnodar, for defendants facing charges carrying penalties of more than 10 years in prison.

In theory, the change was supposed to usher in an adversarial model with prosecutors and defense attorneys on a more equal footing and impartial judges overseeing the process. The system was extended to the rest of the country, with the exception of war-torn Chechnya, in 2003.

Acquittals suddenly became commonplace. Today, defendants such as Kozachenko seize on their right to avoid a bench trial. "The jury trial was my only hope," said Kozachenko, who returned to court last week to hear a judge officially confirm the jury's verdict.

Kozachenko was accused of stabbing to death Larisa Bezrukavaya, the operator of a prostitution ring, and her lover, Alexei Krylov, in Bezrukavaya's apartment on the morning of Feb. 16, 2004, with a motive of theft. At first, the case against him looked overwhelming. He confessed to investigators, and two of Bezrukavaya's prostitutes said they witnessed both killings.

Kozachenko had worked for Bezrukavaya as a driver. According to prosecutors, he came to her apartment when she, her boyfriend and the two witnesses were all present. He immediately stabbed Bezrukavaya in the stomach, prosecutors said. She retreated to the kitchen and then a balcony, where the two witnesses testified they also cowered in fear.

Meanwhile, the witnesses said, Kozachenko and Krylov struggled in a narrow hallway. Krylov eventually was stabbed 13 times. As he lay dying, Kozachenko came out to the balcony, where the witnesses said he stabbed Bezrukavaya three more times in front of them.

Kozachenko then stole jewelry and cash and paid the two prostitutes money they said the dead woman owed them, prosecutors charged, in an attempt to implicate them in the crime. The three then left the scene.

But the prosecution's case was not watertight. It depended mainly on the confession and the two women's accounts. There were no fingerprints or other physical evidence tying Kozachenko to the crime scene, and blood work suggested that the murders did not occur in the manner recounted by the two witnesses, according to the defendant's attorney, Valery Okhotnikov.

During the trial that ended with the third not-guilty verdict, the lawyer told the jury that the failure to produce even a single fiber linked to Kozachenko was "indisputable proof of his innocence." And Kozachenko denied the murders.

In his final argument, Okhotnikov pointed out that the stories of the two witnesses conflicted. He slyly exploited their profession to cast doubt on their credibility, drawing a rebuke from Judge Vyacheslav Plotnikov.

Because of previous Supreme Court rulings, Okhotnikov was unable to directly challenge his client's confession in front of the jury. (Outside the courtroom, he said it was coerced.)

"I leave the confession business without comment," Okhotnikov told the jurors in his final statement, "but we all remember 1937 and confessions" -- a reference to the Great Terror of dictator Joseph Stalin in which millions of Soviet citizens were killed or sent to prison camps, often on the basis of forced confessions.

The comment drew another rebuke from the judge, but some on the jury nodded knowingly as Okhotnikov spoke.

Vladislav Kozachenko, charged with a double murder, was acquitted by a jury for the third time this month. Prosecutors vowed to try him a fourth time. One said of the jury system, "I would abolish it."