The US is gradually building up a DNA data base about everyone, taking samples from everyone who is arrested and all newborns.

Put this together with the fact that false DNA evidence can be constructed to frame someone, and you have a real problem.

At present, scientists cannot identify anything in a person's DNA that would show the person is prone to crime — except a Y chromosome, which shows that the person is male. (Most criminals are male.) In 50 years, maybe that will be possible. The question would be, what is the right use to make of that information?