State authorities arrested and charged Mr. Potts twice within three months. In the first case, he was convicted of battery, resisting an officer and drug possession. In the second case, he was convicted of resisting an officer, drug possession with intent to sell and possession of drug paraphernalia. For these crimes, he received a total of six months in county jail and two years of probation.

Then, in 1998, Mr. Potts sold crack cocaine to a confidential informant who reported to law enforcement that Mr. Potts had a large amount of crack cocaine at his home. A search there uncovered drugs and firearms. He was convicted by a jury and given his sentence by Judge Paine.

Mr. Potts had served over 20 years in a high-security federal penitentiary when the First Step Act became law last December. The First Step Act made the Fair Sentencing Act — signed by President Barack Obama in 2010 to reduce the disparity in sentencing for powder cocaine and crack cocaine offenses — applicable to past cases. The First Step Act also allows a defendant like Mr. Potts to seek a sentence reduction even when the original sentence was for life. The law provides wide discretion to the court to determine whether to reduce a sentence and by how much.

At his sentence reduction hearing, Mr. Potts had much more to say than he did back in 1999. Before me, he was remorseful, dignified and hopeful. He was proud of all that he had accomplished in over two decades in prison — proud of the courses he took in personal growth, responsible thinking, legal research and software, proud of his participation in nearly every health, nutrition and fitness class available. Perhaps he derived his greatest pride from conquering a debilitating addiction and maintaining his sobriety. As his lawyer explained to me, sobriety is not a foregone conclusion in prison, where drugs are widely available.

I wanted to know how Mr. Potts had managed his life in prison. He told me, “A lot of times I felt like giving up, but I didn’t want to let my mom down, my family.”

He continued: “I kept myself away from a lot of people in prison. I wasn’t around the average people in prison. Prison is an awful place. You have all these different types of organizations and gangs and foolishness. That is not me, ma’am. I’m not like that.

“I made some bad decisions in my life," he added, “but I am not a bad person.”

The true marker of a person’s character is what he does when he thinks no one is watching. Because Mr. Potts was sentenced to life, no one had really been looking at what he had been doing. But his unwavering dedication to improve himself over the last two decades, despite his circumstances, convinced me that his hope in his own future wasn’t misplaced.