Thomas Maree-Bey was in his 40s when he began his sixth stint in prison in 2007.
“I was one of those hardheaded ones who didn’t want to do anything but at the end of a sword,” said Mr. Maree-Bey, now 50 years old, who works as an executive assistant at a nonprofit in Washington, D.C.
Criminal-justice experts often attribute the older prison population to harsher sentencing policies and antidrug laws adopted in the 1980s. The conventional wisdom is that enforcement of these laws led to longer sentences and more time served, which, in turn, is rapidly driving up the average age of inmates.
New research, however, offers an alternative view: The population of graying prisoners has exploded in recent years largely because more offenders, such as Mr. Maree-Bey, are entering or re-entering prison in middle age.