The defense is going to claim that his death was not related to kneeling on his back/neck. If you read the body cam transcripts he was complaining of not being able to breathe as soon as he was handcuffed, before he was initially placed in the patrol car. It seems like he was having some sort of medical emergency exacerbated by the stress of being arrested. The first autopsy corroborates this narrative, although the autopsy ordered by the family somewhat disputes it. They're going to claim that the knee on back hold has been commonly used for decades without major incident (demonstrably true) and his death was a result of a combination of drug intoxication, existing heart condition, stress, and probably lingering symptoms of COVID which he is confirmed to have had.

Unless the defense colossally fucks up OR the jurors conspire to agree on a verdict due to societal pressure no one is going to jail for his death.