German Lopez in Vox:
Much of the attention to mass incarceration, including from reform efforts, has gone to low-level offenses, especially for drug and property crimes. In large part, this is likely a result of the media focusing too much on the federal prison system instead of the state prison systems: While about half of federal prisoners are in for drug crimes, only about 16 percent of state prisoners are — and more than half of state prisoners are in for violent crimes.
This is notable because the great majority — 87 percent — of prisoners in the US are housed at the state level, not the federal level. So to greatly reduce incarceration, the country will need to focus on the state level. And to do a lot at the state level, the US will need to reduce the incarceration of violent offenders.
This obviously gets a lot trickier, politically, than addressing low-level drug offenses. A pollconducted by Morning Consult for Vox last year, for example, found that nearly eight in 10 US voters support reducing prison sentences for people who committed a nonviolent crime and have a low risk of reoffending. But fewer than three in 10 backed shorter prison sentences for people who committed a violent crime and have a low risk of reoffending.
“It’s one of the spaces where the policy and public safety arguments are going to have the least impact,” Pfaff acknowledged, “because many will view it as the right thing to do to lock them up forever.”
But there are ways to cut prison sentences for violent offenders without leading to more crime.
For one, incarceration is simply not a good way to combat crime. A 2015 review of the research by the Brennan Center for Justice estimated that more incarceration — and its abilities to incapacitate or deter criminals — explained about 0 to 7 percent of the crime drop since the 1990s. Other researchers estimate it drove 10 to 25 percent of the crime drop since the ’90s. And a 2014 analysis by the Pew Charitable Trusts found that states that reduced their imprisonment rates also saw some of the biggest drops in crime, suggesting that there isn’t a hard link between incarceration and crime.