People seem to forget that in a court proceeding both sides get 1 bite at the apple. Any arguments you don't make at trial cannot be made on appeal a party waives an argument if they fail to make it. You have to make an argument to preserve it for appeal.
You can't decide to forego analyzing evidence and then say well I lost so now I want to analyze it.
If there is evidence a party didn't reasonably know existed at the time of trial that evidence can be considered on appeal. Moreover, scientific advances can allow a scientific examination of evidence that was unavailable at the time of the trial. If science used at trial is undermined by scientific advances that came about after the trial such can be used.
This should be kept in mind when looking at what the defense raises on appeal.
Clemency applications are not limited by such constraints in contrast. So evidence that existed but was overlooked can still be raised in a clemency petition.
