Kevin Ring, president of the prison-reform group Families Against Mandatory Minimums, knows the U.S. prison system intimately.
In the 1990s, Ring worked as a Republican Congressional staffer in both the House and Senate, helping push through a landmark 1994 crime law that established longer mandatory sentences -- including for criminals convicted of non-violent offenses.
Twenty years later, he began serving an 18-month sentence for public corruption and other crimes related to his later lobbying work.
Ring worked at the same firm as Jack Abramoff, the infamous lobbyist whose peddling of influence for cash was so egregious that Congress created a new ethics office in the wake of his scandal.
In 2008, Abramoff was convicted on corruption and tax-related charges and received a four-year sentence.
Ring was convicted in 2010, after an earlier mistrial. After a lengthy series of appeals he began serving his time in a minimum-security facility in 2014.
The turning point in his life, Ring says, "from being a tough-on-crime hill staffer to a defendant," was soon followed by one of the worst: Being forced to explain to two young daughters that he was going to prison.
"Locking someone up in a cage is the worst thing we can do to a person, apart from putting them to death," Ring told CNBC in a recent phone interview.