It could also be acting as a deterrent and thereby preventing the crime. I mean if you're smart, and you know they're going to catch you due to fingerprinting you'd avoid the system entirely.

I'm not saying I agree with the system, but it's the argument that might be used.

Same argument applies to CCTV cameras, you would (and I think do) see a reduction in crime when CCTV are installed [citation needed] (though I believe it just moves to other areas).