Question 1: Where they "religious" before entering the justice system, or was it something that occured afterwards.
Question 2: Are they "religious" because their (grand)parents were and they went to some form of worship as a kid, or were they genuinely following their religion at the time of their entering the Justice system.
Esentially, unless you can show that 95% of people in prison were actively following a religion at the time they commited the crime that got them incarserated, your figures are pointless.
A. But at that point, that comforting blanket utterly fails and comes apart.
How do you tell if your neighbour is really a religious guy or just wants to be seen at church on Sunday? The phenomenon of the crooked merchant who goes to church just because being seen there makes it easier to swindle the rest of the village the rest of the week, is for example mentioned off the top of my head even in a 19'th century novel. It's not a new phenomenon.
Any kind of feeling safer for knowing that that neighbour is actually getting any morals from there, would need one to know what's actually in the head of said neighbour, and becomes basically useless if we can't do that. And, really, we can't.
B. In the same vein, it becomes a claim that's utterly non-falsifiable, and really no better than, say, "The Pharaoh makes the sun rise and the Nile flow."
C. Actually, I'd expect religion to actually make it worse. And I don't just mean the bronze-age precepts inciting to violence, rape, bad parenting, etc.
According to one study, most people seem to work by a sort of keeping the balance scheme. For every good thing they do, they bend the rules a bit somewhere else, and the more important they think they are, the more they bend the rules to their favour too. Think sorta giving yourself your own Christmas present for being a good boy. Sorta.
Or in reverse, basically why people feeling guilty about something go give a few bucks to a few charity, and then don't feel guilty any more. 'Cause, you know, one wrong and one right cancel each other out. Suddenly whatever they did it's no longer a wrong any more, or at any rate no use to think about it any more.
One provable effect for example is that people who drive hybrids, then proceed to break more of the traffic rules at the wheel. They did something as big as saving the planet, they don't exactly expect the rest of the planet to give them a reward for it, so basically they give themselves a bit of exemption from the rules as a reward.
I don't see why that wouldn't apply to religion too. If someone is actually convinced that he's that important (even God particularly loves him and his sect), and he's doing that much of a service to the world (e.g., by witnessing around or whatever), I'd actually expect them to be worse people the rest of the time. Just because of that human nature of keeping the balance.
And by "worse" I don't mean they'd go kill someone, but really, worse than they'd have been without that artificial sense of importance and service done to the world. For each person it's a different point.
