Ok apart from the huge irony where you say we are putting far too many people in prison, and then state the police could deter crime by catching criminals - heaven knows what we are to do with them when they're caught
1) Prison doesn't work because the more liberal in our society have campaigned for prisoners to get more and more rights over the years, that prison is seen as more of a holiday camp than a punishment.
2) Isn't that even more ironic that we aren't catching enough real criminals. I would suggest that the ability to catch the criminals still exists, it's just that the evolution of our judiciary system now makes it harder to prosecute. Taking away the DNA and fingerprint databases will just make things more difficult won't it?
You can't really complain that we aren't catching enough criminals with one breath and then state that the tools that will aid in this catching and prosecution shouldn't be allowed....