I don't want to change the topic, but can you back that up? Can you tell us, specifically, what person in the U.S., say during the past century, was proven to have been wrongly executed by state or federal government? Give us the name, the crime involved, the date, the place, and describe what evidence you think conclusively proved his innocence after his execution. Obviously some people have been wrongly convicted and sentenced. In some cases these may even have been death sentences. But is so, the mistake was discovered before the execution. I have never heard of any person in this country, at least in recent decades, who we know did not commit the crime for which he was executed.
I have seen this stuff before. Someone here once posted a long series of cases from some anti-capital punishment website, supposedly people who had been wrongly executed. But in each case, when you scrutinized it carefully, the supposedly conclusive "evidence" was nothing of the kind. Again and again, the "proof" would be the personal opinion some sheriff or prosecutor offered to a reporter, an ambiguous statement by some other person that might or might not have been an admission of guilt, an alibi provided by someone who was never mentioned at the time by the person convicted, the subsequent arrest of some other suspect, and other sorts of half-baked tripe. To believe this stuff, you have to believe the many appeals court judges involved who carefully reviewed these cases were incompetent.
As for Van Houten, I don't recall exactly what she was convicted of. But if she was proven to have personally taken part in one or more murders, with her own hands, I would be less sympathetic to a request for parole than I would if she had only led cheers from the sidelines, handed someone else a weapon that was used to murder, mutilated someone who was already dead, driven the getaway car, or participated in some other indirect way.