Every time I read about a DNA test that exonerates someone behind bars, I wonder how many people have been locked up for crimes they didn't commit. Sure, they may be bad guys anyway, but how many were locked up solely because they were bad guys and not because of pretty good evidence in the specific case before the jury?
I can't imagine how I'd react if I were unjustly locked up, convicted of a crime I didn't commit. As a teenager I'd sometimes lie to my mother, but I'd get furious when she called me a liar when I was telling the truth. Odd how she would believe my lies, but not believe me when I told the truth. But in those circumstances I had only to stew in my anger, not suffer the loss of my freedom for years on end.
Bad cops, overzealous prosecutors, plain bad luck--there's just too big a possibility that a person innocent of a particular crime (but not necessarily an innocent person, as I said above) could get convicted of that crime. How many people have been wrongly convicted? How many wrongly convicted people have been executed? I shudder just at the thought. DNA evidence should be used whenever it's possible to do so, unlike in the story linked above. And prisoners who have always professed their innocence, but were convicted in the pre-DNA days--I've read about some of them being released after recent DNA tests confirmed their innocence. It angers me, and I'm not even the one who was wronged. They never should have been locked up in the first place.
Freedom is just too important. We have to be sure. And I think DNA testing, when it can be used, is a good step to getting us there.