Does not matter, there have been cases where DA do hide real evidence, have it happened? I can easily bet on it.
There have been cases where there is evidence all over only to find out the real perpetrator years later.
Most evidences is based on just professional opinion, it does not always means fact. Execution based on professional opinion... do you trust these professionals? Lastly there are cases where DA were busted for not being ethical, messed up evidences, favortism, etc is all but too common.
The ONLY time I support execution is when perpetrator actually commits horrendous crime and gets executed at that moment, location of the crime scene. Its almost impossible to make mistake when one raped a child and gets killed at the spot, that's the real justice, not bust later on and get executed.
