“Maybe somewhere down the line Congress will relieve the people in your position,” he said to Mr. Walker, then 26, at the sentencing hearing in 1998. Today Mr. Walker is 41, and Judge Gilbert looks back on the sentencing as “one of the most difficult moments in my judicial career.” The judge, a former prosecutor, has written a letter toPresident Obamasupporting a commutation of the sentence, and praising Mr. Walker’s record as a model prisoner.

“His unbroken spirit in the face of a life sentence is an example of the human spirit at its strongest,” Judge Gilbert wrote. “As a judge, as a citizen and as a taxpayer, I see no reason that this individual should spend the rest of his natural life incarcerated.”

REYNOLDS WINTERSMITH

After the drug-related death of his mother, a heroin addict, Reynolds Wintersmith moved to his grandmother’s home, which was a brothel and a crack house. There, as a teenager, he was taught to cook crack by his aunts. He spent a little more than a year in a drug ring selling crack in Rockford, Ill., until being locked up shortly after his 19th birthday on drug-conspiracy charges.

Image Reynolds Wintersmith

“You were 17 years old when you got involved in this thing,” Judge Philip G. Reinhard said to Mr. Wintersmith when he imposed the mandatory sentence in federal court. “This is your first conviction, and here you face life imprisonment. I think it gives me pause to think that was the intent of the Congress.” He urged Mr. Wintersmith to “hope something will change in the law.”

Mr. Wintersmith is now 38 and has spent half his life in prison, becoming a highly regarded tutor and counselor who helps other prisoners prepare to return to society. He looks back on his teenage self as a social menace but also as someone quite foreign. “I am no longer that person,” he said. “I ask only for a chance to contribute as a positive, productive human being in society.”

ROBERT RILEY

Robert Riley was a follower of the Grateful Dead who sometimes sold drugs to fellow Deadheads in the 1970s and ‘80s. Convicted several times for possession of small amounts of marijuana and amphetamines, he spent short periods in county jails in California and Wisconsin. In 1993, he was convicted in a federal court in Iowa of conspiring to distribute hits of LSD dissolved on pieces of blotter paper.