A couple of years ago The New York Times noted that the percentage of criminal cases ending in plea bargains has increased during the last few decades as mandatory minimum sentencing laws have raised the potential penalty for going to trial. A new report from Human Rights Watch highlights the tremendous leverage that such laws give federal prosecutors in negotiating plea deals with drug offenders. Under Title 21, Section 841(b)(1), for example, prosecutors have complete discretion in deciding whether to mention prior felony convictions in connection with a drug offender's sentencing, which can have a jaw-dropping impact on the penalty he receives:

If a prosecutor decides to notify the court of one prior conviction, the defendant's sentence will be doubled. If the prosecutor decides to notify the court of two prior convictions for a defendant facing a 10-year mandatory minimum sentence on the current offense, the sentence increases to life.

That is what happened to Sandra Avery, who in 2005 was arrested for possessing 50 grams of crack cocaine—less than two ounces—with intent to deliver. That amount alone triggered a 10-year mandatory minimum sentence, and that is the penalty she would have received if she had pleaded guilty. Instead she went to trial, was convicted (as are 90 percent of federal drug offenders who insist on their right to trial), and received a life sentence after the prosecution called the court's attention to Avery's three prior convictions in Florida for possessing small amounts of crack. The crack involved in those earlier offenses was for personal use, and it was worth less than $100 all together. "Among defendants who were eligible for a sentencing enhancement because of prior convictions" in 2012, Human Rights Watch found, "those who went to trial were 8.4 times more likely to have the enhancement applied than those who pled guilty."

Another powerful source of prosecutorial leverage is Title 18, Section 924(c), which prescribes mandatory minimums for possessing a gun in connection with a drug offense. The first such offense triggers a five-year sentence, each additional instance triggers a 25-year sentence, and the sentences must be served consecutively. That is how Weldon Angelos ended up with a 55-year mandatory minimum sentence for three small-time marijuana sales during which he possessed a gun, even though he never threatened or hurt anyone. Before Angelos was convicted and received what may well amount to a life sentence, prosecutors offered him a plea deal that would have resulted in 40 fewer years behind bars. "Among drug defendants with a weapon involved in their offense," Human Rights Watch reports, "those who went to trial were 2.5 times more likely to receive consecutive sentences for §924(c) charges than those who pled guilty."

The impact of such disparate treatment is dramatic:

In 2012 the average sentence of federal drug offenders convicted after trial was three times higher (16 years) than that received after a guilty plea (5 years and 4 months)….Among first-time drug defendants facing mandatory minimum sentences who had the same offense level and no weapon involved in their offense, those who went to trial had almost twice the sentence length of those who pled guilty (117.6 months versus 59.5 months).

Prosecutors have always offered lenience in exchange for guilty pleas; that is what makes such arrangements possible. But the huge differences in punishment documented by Human Rights Watch make demanding a trial so risky that almost no one chooses that option. "Only three percent of federal drug defendants go to trial," the report notes. "Plea agreements, once a choice to consider, have for all intents and purposes become an offer drug defendants cannot afford to refuse."

In the July 2011 issue of Reason, Timothy Lynch explained the pernicious impact of plea bargaining, noting that the popular understanding of American justice "is wildly off the mark" because only a small percentage of cases actually go to trial.