I recall a homicide case where the defense argued that the victim shouldn't have died. The defendant hadn't hit him all that hard. The victim had an egg-shell skull, which the defendant had had no way of knowing about.
The court held that the perp was the one who selected the victim. You are guilty of homicide if the person you hit dies from the blow that you hit him with.
If we apply that logic, Floyd's use of drugs doesn't amount to a defense.
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Irrelevant footnote: If that perp actually had enough head-hitting experience that he could offer expert testimony as to whether his blow should have killed, then I definitely want him to have been convicted.
He argued that Chauvin followed his police training and should be found not guilty.
I recall another case. A miner fell down a mine shaft; the mining company was sued.
Plaintiff claimed negligence: A vertical drop that wasn't barricaded or lit.
Defense claimed that it was in compliance with industry standards, which was they had to show.
The court held that an unbarricaded and unlit shaft was egregious. Yes, the law--as previously understood-- called only for compliance with industry standards, but this was a case in which industry standards were patently wrong, so that standard did apply.
If we apply that logic, then even
if Chauvin was doing what he was trained to do, that may not amount to a defense.