I find it interesting that some (all?) of the states have life or death sentences for people who have murdered someone, when the research says the chances of a murderer re-offending for violent crime is less than 3%, and there is research in California cited here:
"Mullane said she was able to determine that 988 convicted murderers were released from prisons in California over a 20 year period. Out of those 988, she said 1 percent were arrested for new crimes, and 10 percent were arrested for violating parole. She found none of the 988 were rearrested for murder, and none went back to prison over the 20 year period she examined.
'That's the lowest recidivism rate. That's unheard of," Mullane said. "In 20 years, the chance of you being returned on another murder was zero.'"
That captured only a 20 year period only in California, but given other extremely low stats, it isn't a stretch to generalize with a margin of error. Each participant spent no less than 20 years in prison and were very good at convincing parole board members to release them after "only" 20 years.
It is actually that much safer to release murderers over people who commit property crime, and yet for property crimes with $2,000-$10,000 damage, it's punishable by up to only five years. Over $10,000 damage is punishable by up to ten years. Those who commit property crime are the most likely to re-offend, with 77% recidivism.
All that to say that prisons are little more than a campaign tool for politicians to win public approval by getting tough on murderers and violent criminals because they play on the public's need for a sense of safety, even if that is a false sense of safety. Sure, they hope that a little prison time deters the criminal from re-offending, but they already know they will. In addition, prisons are set up so that people will fail. Prisons, corrections, justice systems are big money-makers, employ a lot of people and appease the public (in the US, anyway. In Canada, they are publicly funded and the government wants to keep employing all those people who pay high taxes from their high incomes, so they set people up to fail). Social structure is set up deliberately to keep people within the station of life into which they are born. There are rags-to-riches exceptions but only to give the poor and common folks "hope."