ANTHONY YARBOUGH was convicted of a triple stabbing in 1992, although not a speck of blood was found on his clothes and the DNA under one victim’s fingernails did not match his. He was found guilty because his petrified 15-year-old co-defendant, Sharrif Wilson, pleaded guilty and testified against him in exchange for a lighter sentence. (He later recanted.) The same DNA was found on the corpse of another stabbed woman while Mr Yarbough and Mr Wilson were in prison. Yet they were not exonerated and freed until this year.

More than 95% of convictions in America are reached through plea bargains, in which the defendant agrees to plead guilty in return for leniency. Many convictions also depend on the testimony of a “co-operating witness”, who snitches for the same reason. Defenders of the system argue that it is efficient. By avoiding long, costly trials, America can lock up lots of villains. Without plea deals, the courts would be swamped.

Alas, the process is open to abuse (see article). Prosecutors hold all the cards. If a defence lawyer offers a witness $100 for a false alibi, he is guilty of bribery. But if a prosecutor offers a co-operating witness something far more valuable—the chance to avoid several years in a cell—that is just fine. With so much at stake, snitches sometimes tell prosecutors what they want to hear. One study found that nearly half of the cases in which people have been wrongfully sentenced to death hinged on false testimony by informants, typically criminals who were rewarded with lighter punishments.

Over the past generation, two things have given prosecutors more muscle. One is the proliferation of incomprehensible laws, which mean that in complex white-collar cases a prosecutor can usually find some technical rule his target has broken. The other is the spread of mandatory minimum sentences, which transfer power from judges to prosecutors. In Florida, the minimum sentence for possessing 4-14g of heroin is three years; for 28g or more, it is 25 years. Thus, it makes a huge difference whether a dealer’s girlfriend is charged just for the drugs in her handbag or also for the stash in her boyfriend’s safe. Likewise, a white-collar defendant may face one count of fraud or a separate charge for every e-mail sent in pursuit of it. In both cases, it is up to the prosecutor to decide.

Eric Holder, the attorney-general, who announced his retirement on September 25th (see article), has urged federal prosecutors not to seek such harsh sentences in some drug cases. But only some; and state prosecutors are still free to threaten defendants with terrifying punishments if they fail to plead guilty or implicate others. A federal judge recently guessed that thousands of innocent Americans could be stuck behind bars because of coercive plea bargaining.

Let judges judge

Many other countries ban plea bargains or limit them stringently. Ideally America should ban them too. If it cannot face the thought, it should at least reform them. Mandatory minimum sentences should be scrapped, and judges should judge each case on its merits. Prosecutorial control over plea bargaining should be loosened, for instance by bringing in a magistrate judge who could take offers from both sides and act as adjudicator. This would make the negotiation more of a give-and-take, and could be used to shine light on a process that is currently as murky as it is inequitable.

As America’s military dominance declines, its influence will depend more and more on “soft” power: winning friends because of the attractiveness of its ideals. Its justice system makes this difficult. Mr Holder’s successor should try much harder to rein in America’s over-mighty prosecutors.