This Isn't Really A Defense, Either

In theory I understand what's being argued in the argument George Floyd's cause of death. But I marvel at the absurdity of the idea that Floyd's body finally gave out from drug use at the moment a cop was kneeling on his chest and compressing his diaphram so he couldn't breathe.

— Josh Marshall (@joshtpm) April 8, 2021

If I recall my torts law classes correctly (and Crim Law, but I never practiced the latter, and law school was many decades ago), there is a settled concept in law that you take the victim as you find them.

So if your negligence is the cause of an injury, and it turns out the person you injured had a weak heart (a Hollywood scenario, granted) and dies subsequent to the injury and because it exacerbated an underlying condition, you are responsible for the wrongful death.  You don't get out of it by arguing "I didn't kill her, her heart did!"

Everything in a trial depends on the jury charge.  So the defense may be hoping to get questions to the jury that include some exculpation for pre-existing conditions in George Floyd.  Odds are that won't happen (never say never, but I think the rule about what you did and what they suffered not being an escape hatch, holds), but they hope to get the jury to decide to answer the questions put to them in a way that lets Chauvin off the hook because, after all:  drugs.

It's an appeal to ignorance and probably racism (black people use drugs, which make them superhuman, or more than they already are, and people who use drugs deserve the wages of their sin, which is death).  It's also a Hail Mary (as in a pass you throw and pray is caught by your guy).  

The law, in other words, doesn't allow for such an absurdity; not as a matter of law, anyway.  Whether the jury finds it to be a fact (as in finding Floyd didn't die because Chauvin knelt on his neck for 9 minutes) is another matter.

That's why the prosecution is putting on evidence like this, though:

Dr. Martin Tobin: "Mr. Floyd died from a low level of oxygen. And this caused damage to his brain that we see, and it also caused [an arrhythmia] that caused his heart to stop." #ChauvinTrial pic.twitter.com/6DRnCToTEs

— Aaron Rupar (@atrupar) April 8, 2021

Gotta give the jury a reason not to buy the bullshit.  And they probably aren't:

Dr. Tobin says that in the image on the right, it’s visible how Chauvin has increased the pressure leading to more severe compression of the hypotharanx. Compares trying to breathe like this to “breathing to a drinking straw...except it gets way worse than that” pic.twitter.com/AUHobHawKv

— Unicorn Riot (@UR_Ninja) April 8, 2021