Not to challenge you, but, do you, or any of your friends, have some statistics to show the ratio of those innocent but executed versus those who were truly guilty and executed ?
That is why there is a long drawn out system of appeals, I think. To provide those sentenced to death the opportunity to be heard by higher courts, and the evidence against them reviewed, and the sentence commuted or overturned if needed.
On the investigative level, I think that to avoid execution of innocent persons, if it is proven during appeals, or if it turns out after the fact of execution, that the convict was innocent, then repercussions ought to be felt all the way down to the investigating officer and all the way up to the prosecution.
Fire them, deny them retirement benefits, strip them of all honors, and then send them to jail: FOR LIFE without the possibility of parole.
That ought to stop fabrication of evidence, or personal motives, or sloppy detective work.