From M’s POV, Z would have had to have pulled a weapon and not just a cell phone to justify a punch in self defense.
Otherwise, a lot of folks would be running around breaking other folks’ noses just because the other folks pulled out cell phones during a conversation. Carried to the extreme, the use of cell phones would need to be tempered with the warning that pulling one out of one’s pocket is inciting other folks to punch the cell phone user in the nose.
Also I am not yet clear on what possible good motivation could be for slamming someone’s head into the ground while on top that person. If the person being (..ahem..) mounted has a deadly weapon, then it seems most logical that the person on top should grab the weapon to attempt to neutralize it, otherwise one risks being injured by the weapon. On TV fiction crime shows at least, a close combat struggle between two people with a weapon always has the weapon as the center of the struggle, and no one ever to my recollection ever goes for the armed person’s extremity over the armed person’s weapon. Those struggles are always depicted as ending either in one person being injured or killed by the weapon, or in the weapon being taken or tossed away by the other person.
What is at issue is whether Z is guilty, not M’s guilt or innocence. While I think your physical scenario is plausible, and usable by the defense, I would not spend much bandwidth trying to let M off the hook for escalating. To me, the possibility of unjustified escalation to physical violence by M upon seeing Z reach for a cell phone would suffice for reasonable doubt of the prosecution’s scenario.
What is the MMA version of the “use of force continuum”? I imagine that the MMA fighting style does *not* take into consideration the possibility that one combatant may be armed with a deadly weapon. Perhaps also the MMA fighting style presupposes that the fight occur on a soft martial arts mats such as made with 1” thick closed cell high density EVA foam rubber here:
http://www.rubberflooringinc.com/interlocking-tile/foam/1-jumbo-soft-tile.htmlwAqQ
Imaginably, as a 17yo, M not only was not totally aware of his own strength, but also less than fully aware of the lethality of his MMA fighting technique when performed outside of a professional MMA ring of the type that he probably had opportunity to see used only on TV. He was obviously not counting on Z being armed.
This might be part of what the public who is sympathetic to Z is enraged about at the core: the unrealized mismatch of intentions and mismatched levels of maturity, leading to fundamentally different potential POVs by M and Z during the incident. M might have wanted to hurt Z severely, and attempted to do so unjustifiably, using immature judgment (assualt, escalating to assault using deadly force). This view emotionally does not take into consideration Z’s POV, that of an immediate need to respond with deadly force to an apparently adult assailant using potentially deadly martial arts skills to inflict mortal damage. However, in the ‘continuum of force’ model, that view may be considered reasonable, and permitted. Admittedly, Z is not an LEO, so the continuum of force model does not apply in totality, but what may be needed for these types of situations is a SYG analog to the continuum of force model. With such a model, the police, DA, and public can understand similar incidents better when they occur (and perhaps help avoid yellow journalism defamation, show trials, malicious persecution, and street riots in the future).
Admittedly, Z is not an LEO, so the continuum of force model does not apply in totality...
All that is necessary for Zimmerman to have acted in a justifiable way is: Did the other party initiate the actual fight, and did Zimmerman reasonably fear that he was at risk of death or serious injury?
That's it.
Based on the evidence presented, I would say the answer to both questions appears to be yes.
The answer to the first question is not absolutely, 100% certain. It is PLAUSIBLE, though not at all likely, that Zimmerman COULD have thrown the first punch.
That would undermine the claim of self-defense.
But there is absolutely no hard evidence in favor of that, and there is CERTAINLY more than a reasonable doubt against it.
The answer to the second question appears to be an indisputable YES.
I see no sane way to return any verdict other than acquital. At this point the case appears to be so weak that it should NEVER have come to a trial.