I may be mistaken regarding the details of those three incidents, but none of them received the Death Penalty. The Death Penalty is handed down by a judge in accordance after a jury convicts them of breaking the law.
That was my point...
~Jeordam
Your memory is faulty. Trayvon Martin didn't have a gun to attack anyone with. He was walking home.
Sandra Bland refused to put out a cigarette in her own car, which, as far as I know, no law permits the police to demand in response to a traffic violation.
As for Michael Brown, it was more than just failure to comply with an officer's order, but again, I don't know of anything there that qualifies for a death penalty, and certainly, that makes no sense in a situation where there was no court involved in the decision.
In all three cases, especially with Bland and Martin, their own actions did not cause their deaths.