Wow, 17 death row inmates in the past 22 years have been exonerated with DNA testing. Less than one per year. Impressive!
Have you ever considered the fact that the majority of death row inmates were convicted WITHOUT the necessity or need for DNA evidence?
Ever heard of eyewitnesses?
Ever heard of fingerprints?
Ever heard of confessions?
Ever heard of jailhouse snitches?
Ever heard of sting operations?
Ever heard of paid informants?
Ever heard of undercover FBI agents and police officers and ATF agents?
Maybe in your world, killing should only be done by criminals, but in my world, any killing done by criminals makes these criminals automatically eligible for extermination via capital punishment laws. An eye for an eye.