Federal prosecutors twice offered suspected heroin trafficker Roy Clay a deal: plead guilty and serve 10 years.

Clay turned them down.

When a jury found him guilty, a reluctant judge had no choice but to send him to prison for life.

Because prosecutors had brought up two previous drug convictions in his case, Clay was subject to an "enhanced mandatory minimum" at his sentencing in August. Many other defendants, facing similar prospects in federal court, have elected to make a deal.

The Justice Department says it is moving away from the use of enhanced drug sentences for some offenders. But critics say cases such as Clay's show the amount of power still wielded by federal prosecutors, who retain the authority to construct fearsome sentences and pressure defendants into guilty pleas.

Plea bargaining, in which both sides make concessions to resolve a case with certainty and speed, is a key part of the criminal justice process. But a report issued Thursday by Human Rights Watch says enhanced sentencing has left defendants few options at the bargaining table.

Even some innocent suspects might be persuaded to take a plea offer, the New York-based rights group said, though it did not describe any instances of that happening here.

"The bottom line is, you either cop a plea or pay the price," Jamie Fellner, the report's author, said in an interview.

Sentencing data show that the harshest mandatory sentences are rarely imposed in Maryland. But Human Rights Watch argues that their mere existence puts pressure on criminal defendants.

Federal prosecutors have several weapons to wield when bargaining over pleas. They can name different drug amounts to trigger mandatory minimum sentences, and can use other filings, based on a defendant's criminal history, to lengthen prison time. Judges do not usually have the authority to review those outcomes.

This summer, the Justice Department instructed federal prosecutors to consider more carefully whether defendants deserve the weightiest sentences the law allows. Defense lawyers and activists welcomed the policy shift, but ask whether it offers firm enough guidance, and say change has been slow.

Edward Smith Jr., Clay's attorney, said he all but stopped taking federal cases when the new drug sentencing laws were introduced in the 1980s because he felt the chance of a fair outcome was so slim. Smith said he now sees some light at the end of a three-decade-long tunnel.

"We're not talking about guilt," he said. "If you do something that's against the law you should pay the penalty. But it should not be so out of whack. … It wipes out generations of people who could help themselves back into some sort of productive life."

Fellner, the author of the report, said prosecutors told her they feel compelled to seek the longest sentences available to them when cases go to trial to strengthen their bargaining position in other cases.

Steven H. Levin, a former federal prosecutor in Maryland who now works as a defense attorney, pointed to one of his clients who succumbed to the threat of a long mandatory sentence.

Anthony Marcantoni was caught receiving shipments of between 50 and 250 pounds of marijuana in the parking lot of the Mount Washington Whole Foods.

In a case such as Marcantoni's, which involved a metric ton of marijuana, a previous conviction on certain qualifying charges can trigger a 20-year sentence.

Marcantoni opted to plead guilty, Levin said, "because of the potential downside and the outrageous amount of time he was potentially facing."

He was sentenced last year to 10 years and one month in prison.

Two prior convictions on a qualifying charge can lead to a life sentence. Still, Clay — whose case involved a kilogram of heroin — took the gamble and went to trial.