I think at least with advances in science and forensic technique, the amount of people wrongly convicted and placed on death row has decreased dramatically. At least I should hope so.
CNN Investigates did a great show on how inept/corrupt nationwide the DNA-crime labs are.
Ie handling of OJ evidense (shudder). This happens far too often. They went around the county, it's a joke how many are substandard or flat out corrupt.
Prosecuters? Quoted one "I'm looking to get a conviction. If the crime lab messed up on the DNA processing i do not want to know about it".
I know a defense lawyer and he tells me without a doubt,
every time in the chain of handling of DNA there is a hole to poke.
So "they have the DNA" is hardly a slam dunk.
Also went over how easy it is to plant DNA, frame someone.
Scary. Keep an eye on Joe or Wolfy if you notice your disposible razorblades are missing from the trash.