As an undergrad, I felt lucky to nab an internship in the U.S. Attorney's Office at the Department of Justice. The job wavered between dull and discomfiting: listening in on prisoners' phone calls and attempting to identify the faces of 'suspicious' individuals on city surveillance camera footage.

But my biggest project was "Joe." Joe had a record; he'd been caught selling crack a few years before. He also had a conviction for a robbery in a different state when he was only 19. He got arrested again in the poor neighborhood where he lived, and a jury once again found him guilty of possession with intent to distribute crack cocaine.

A lowly intern, I worked diligently for a month, gathering all the evidence against Joe from his jury trial. A few days after my semester came to a close, the day of the sentencing hearing arrived. I was excited. I was young and degree-less, and I was going to get to see the culmination of my efforts in a U.S. District Court. I wore my best suit and heels and bragged to my parents about my plans for the day.

The government invoked the 1984 Armed Career Criminal Act (ACCA). Justice lawyers argued that Joe had three strikes against him. The judge was obligated to give Joe the mandatory minimum of 15 years. But prosecutors wanted more. They wanted Joe locked up for as long as possible, claiming that he was a danger to the community.

I arrived early and sat behind the prosecutor. Doors in the back right corner of the room opened and there—in chains and a jumpsuit—was Joe. I had seen pictures of him and even heard his voice many times while working with his case. But when I saw him in the flesh for the first time, my enthusiasm and pride congealed into something far more unpleasant—qualms about the justice and efficacy of the criminal justice system I'd been suppressing suddenly came to the forefront of my mind.

Even before my internship inside of the Department of Justice, I knew that the U.S. incarcerates too many people, often for long terms that don't match up with the severity of the crime, but it was never real to me until that moment.

The hearing was over quickly. Joe got more than 25 years in federal prison, plus 6 years of post-prison supervision and a faintly ridiculous $3,500 in fines.

As I walked out of the courtroom, I knew the prosecutors were probably disappointed: Even though the judge had given Joe 10 years more than the law required, they'd asked for a full decade more. I was overrun with guilt. I had done that to Joe. Sure, I hadn't done it alone. But I'd worked hard to get a man locked in a metal cage for a quarter century and until right that minute I'd been unambiguously (and maybe even a bit smugly) proud of myself for it.

Now I'm trying to make amends. I have a new gig working on criminal justice reform for the Reason Foundation, the nonprofit that publishes Reason, doing research to help curtail overcriminalization and mass incarceration of Americans. I am working on state-level statutes and legislation that can be reformed to ease the strain on overpopulated prisons, overburdened taxpayers, and non-violent offenders. I regret my work compiling that file on Joe, but the reports I assemble from now on will be very different.