The meeting made me proud of his accomplishments, but sad that I had not been more confident in him. He still had several years left on his sentence, but it was clear that he had served enough time.

After I returned to my office, I contacted the prosecutor and his lawyer and encouraged them to find a way to get him released early. But they told me there was no straightforward way to shorten a federal inmate’s sentence, even if prison officials acknowledge that more jail time is a waste of time and money. So he had to stay in prison, at an annual cost of $30,000 to taxpayers.

The tragedy of mass incarceration has recently focused much attention on the need to reform three-strikes laws, mandatory minimums and the federal-sentencing guidelines, which often direct judges to impose excessive sentences. We also need a mechanism for judges to re-evaluate the sentences they’ve imposed.

It’s true that federal prisoners can earn up to 15 percent off the length of their sentences if they stay out of trouble. But this doesn’t incentivize prisoners to take advantage of work or study opportunities.

Instead, Congress should enact legislation that would allow every sentenced defendant one opportunity to petition his sentencing court for a reduction based on extraordinarily good conduct and rehabilitation in prison.

This “second-look review” should be available only to prisoners who are supported by their wardens. To minimize the increased workload on busy federal judges, each prisoner should be allowed only a single opportunity to seek early release and do so only after serving at least half of the sentence imposed (or two-thirds of a mandatory minimum sentence).

Factors in support of an early release should include more than just clean disciplinary records in prison. Job readiness, success with drug treatment, completion of vocational and educational training and extraordinary family or health circumstances should count as well.