The United States spends nearly $7 billion a year to operate a network of federal prisons that house more than 200,000 inmates. About half of them are incarcerated for drug crimes, a legacy of 1980s laws that prosecutors use to target not only kingpins but also low-level couriers and girlfriends. Multiple convictions for small-time offenses under those laws mean thousands of people are locked up for decades, or even the rest of their lives.

This year, everyone from Attorney General Eric Holder to Tea Party Republicans in Congress has argued that those stiff mandatory minimum prison sentences do more harm than good for thousands of drug offenders. Legislation to cut the tough-on-crime penalties has stalled on Capitol Hill, but it's likely to be reintroduced in 2015. Meanwhile, the White House and the Justice Department have taken the unprecedented step of asking for candidates who might win early release from prison through presidential pardons or commutations in the final years of the Obama presidency. That effort, known as Clemency Project 2014, is moving slowly.

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