Honestly, his past has nothing to do with his murder. It won’t even be presented at trial.
McMichales committed the act of “aggravated assault” a felony in the state of Georgia, the only man legally can defend himself and claim self defense was Arbery.
I believe Travis believe Arbery stole his gun out his truck and believe he had it, that is why he was trying to stop and murdered him because Arbery wouldn’t submit to his demands.
It would be also the reason why Travis trapped Arbery on the other side of the truck and pulled the trigger quickly before Arbery could pull the gun Travis belied he had.
It is why Gregory McMichales admitted to police that he searched Arbery’s body looking for a gun.
That is my theory, we shall see if I am correct or not.
You are certainly correct in that Arbery's past is completely inadmissible in a court of law - if they were actually following the laws.
By that same notion, Arbery forfeited any claim to "self defense" when he ran up and attacked Travis, which he rather clearly did. It's all on the video.
The situation devolves into "mutual combat". At most, Travis McMichaels goes down for an "involuntary manslaughter" charge. Possibly he walks on his own "self-defense" claim. Murder conviction? No.
That's all if they were were actually following the law. Which they are not.