I can answer this based on my own experience.
I WAS an addict, ive been clean for over 1 year. March 18th will be one year since i got out of jail. life is great now.
I think it depends on a lot of different factors.
As far as rehab is concerned, i think that rehab would be a better bet, if the person just started using. however if their using is what got them into trouble its probably to late for rehab.
As far as jail is concerned, depending on the crime, rehab might be better. But it is the wake up call of all wake up calls.
In my personal experience, i went to jail about 3 times, and didnt stay clean after i got out, however i only did 1 month each those times.
What really did the trick was the time i just spent in jail, almost a year.
I know that when it comes to drugs and getting clean, you need more than just one month in rehab, and they usually dont keep you for that long. Being in jail, took me away from my "life" i was leading. It gave me time to think about my life and everyone i have hurt.
I know that the only way someone will get clean is if they WANT to. And if they do, they need a whole life change, and to be away from it long enough, and clean longer than 3 months, before they should be allowed to reintegrate themselves back to their own life.
There are many things out there that can help people, IE: N/A, A/A, counseling, phychiatry, etc.
Be forewarned, N/A, while it helps a lot of people, it doesnt help everyone, they surround themselves with their former addiction, while this helps to teach people how not to repeat the same mistakes, they are nevertheless reminded of that life style, and at meetings there is a lot of drama. i went to N/A for 10 years, and never stayed clean, but this time i didnt go and stayed clean longer than i ever have. But if you go you will find people who have been clean for 5+ years and more. Like i said, and i have nothing against N/A-it is good, but it works for most and not for some.
I hope this helps,
Drug addiction is a trying time on family and friends. and the person using.
I wish the best.