The evidence is really that the more intense the intervention in a young person's life—i.e., the more intrusive police are, the more frequently they're charged, the more court appearances they have, the longer sentences they have—the worse the outcome, the worse the recidivism, the slower rehabilitation will be.
I hate to say this, because it would mean we could all just go home, but an awful lot of what we have to do for young people is just keep them safe till they grow up. They will outgrow violence. They simply will. They'll have kids and a mortgage, and they will be too tired to be climbing over fences or doing any of that stuff. So some of it is just keep them safe, train them, support them, educate them, give them all the resources they need. That will produce the best outcome.
You asked about increases in crime. There are pockets; there will always be pockets. Maybe the factory closed and a bunch of parents got laid off and the families are poorer. There could be a multitude of reasons, but there will always be pockets where there are increases in various types of crimes. You'll see that car theft goes up in one neighbourhood but there are gangs and there is gang violence in other neighbourhoods. Does length of sentencing affect that? No.
I think you asked a third thing, about evidence, and I'm afraid I've forgotten it.