The FBI is not run with the same care that most hospitals are.
The goal of the hospital is to cure the patient.
The goal of the FBI should be to find the culprit.
But the problem is that most of the time there is just one suspect, and they assume the goal is to find the evidence to convict him.
If the doctor screws up, he can get sued and will see it as a defeat.
If the FBI lab fails to verify the evidence presented by the agents, they could lose their jobs.
DNA is pretty straightforward, but it takes a lot of care to make sure that the evidence is not contaminated, and much of the contamination is invisible and cannot be detected by anyone but experts.
Still by using DNA as evidence, I think that the possibility of convicting the wrong person are less.
