Criminals commit crimes because they think it's a good idea at the time. They think it's a good idea at the time, because factoring in time discounting, they prospect it to be one.
Now, Jamal has a very high time discount rate and he's not so good at prospecting. These two things are highly correlated and the latter is probably not very changeable in
The problem most forms of restorative justice run into is that they never consider that Jamal was acting in his perceived self-interest, which is something like the most obvious thing ever. But, it still gets missed and instead criminal actions are understood as some always curable pathology; a kind of extricable cancer of the mind that can be removed by hugs, positive feelings and a minimum wage job.
Sometimes this kind of stuff can work, maybe you can stop Jamal from hosing down a block party on south side through a court ordered mentorship program. But, more likely this kind of stuff will fail, especially when the crimes are less retarded -- think any crime where the pay off is more than just cathartic.
Worse still, most programs are going to lack intelligent incentive structures; it doesn't matter if my youth outreach/reintegration program is totally useless, because no one will pay that close attention and outcome monitoring is guaranteed to be dog shit. Also, there's never going to be anything to replace it with except another dog shit, also totally ineffective scheme. If you're lucky, you'll rediscover the wheel after ten years and go back to sending everyone to the slammer for 9 trillion years. There might exist a program that would kind of work. However, you probably won't find it and the incentives at play aren't to reduce crime, but to get paid and any program is going to be highly dependent on the quality of the implementation.
In the end the cold hard truth of the matter is that sending people to prison reduces crime and sending them to prison for longer reduces crime even more. There's a strong argument for not sending people to prison for things that aren't really significant crimes, or that don't betoken a general proclivity towards criminality. But even then the solution is not "restorative justice," but just other kinds of sanctions that don't disrupt their lives as much or put them into contact with worse offenders. Honestly, punishment for minor drug possession offences should just be caning, no prison, just a dozen strokes of the cane.
There is also no fact of the matter on whether this or that is "just"; justice is just a question of (usually self-serving) expectations. Confront the problem of crime on the basis of what minimizes crime, not whether this or that is "just" or whatever. Justice is basically just a matter of consistency.