It's long been common knowledge that prisons often act to train inmates to be better criminals rather than to reform them. The thing about "common knowledge", though, is that is often turns out to be wrong, so it's important to keep researching it.
At least for now, that particular bit of common knowledge is strengthened, not over turned. NPR's "Morning Edition" reports on a study showing how crime does pay, for those who study it in prison. When Crime Pays: Prison Can Teach Some To Be Better Criminals
Included in the survey are questions about how much money individuals make legally and illegally. Because the survey also ascertains whether people have spent time in prison, Hutcherson pored through data from tens of thousands of queries to a large number of young people to establish whether illegal earnings went up or down after individuals served time.If prison reformed criminals, illegal earnings once people were released ought to have gone down. But if prison was a "finishing school" for criminals, illegal earnings after serving time should have increased.
"Spending time in prison leads to increased criminal earnings," Hutcherson says. "On average, a person can make roughly $11,000 more [illegally] from spending time in prison versus a person who does not spend time in prison."
Also interesting is a comment at that site by a reader using the name Frank Winchester, describing his experience after a DUI arrest:
Not being able to post the required bail bond, I was remanded to a county jail (Cook County, Illinois) to await a court date.
While there, I learned in the first three days how to; field test a diamond with a wet piece of toilet paper to check for flaws; tell if an oriental rug is worth rolling up and stealing (and if it is, to call the fence and negotiate a price before taking it from the home); hot wire a home or business alarm system; "slim jim" and hot wire a car and find a fence late at night.