I see your point, but I'm not sure to what extent this would be probative (nor do I know how the actual chain of custody and discovery process actually played out, so I can't comment on whether the prosecution fell short on its responsibilities or not).

The basis of my reservation, which may seem extremely pedantic, is twofold:-

First, it's undisputed that Zimmerman spent several minutes following Martin while commenting on his suspicions to the police dispatcher. At some point Zimmerman exited his car, came face-to-face with Martin, and then they had an altercation. It seems quite plausible to me that Martin might have punched Zimmerman in the nose as alleged.

But it's not the case that Zimmerman was doing his own thing, ran into Martin, and was attacked by him. Rather, we know from the recorded phone call that Zimmerman followed Martin for at least two minutes in his car, at which point Martin ran away and Zimmerman got out of the car and began to follow him (per http://en.wikipedia.org/wiki/Shooting_of_Trayvon_Martin which has the audio recording). Under Florida law (http://law.onecle.com/florida/crimes/784.048.html), Zimmerman's behavior up to that point amounts to at least harrassment, and arguably aggravated stalking; it was certainly reasonable for Martin to believe that Zimmerman, through his actions alone, presented a credible threat to him.

Whether Martin was a peaceful person or not is thus (IMHO) mooted by the undisputed fact that Zimmerman was chasing him. Running away from another person is the exact opposite of an aggressive posture. Pursuing a person who is running away, by contrast, places the object of pursuit in a defensive posture. One could certainly argue that when Martin approached Zimmerman's car to 'check [him] out' and then ran away, that he had misapprehended Zimmerman's lawful intentions. But when Zimmerman got out of car and started running after him, that could only be interpreted as a threat. The act of pursuit made the situation into a conflict, in which Zimmerman was the aggressor.

It's worth considering what the outcome of this would have been had Zimmerman not shot Martin as he did - ie, supposing Martin had punched Zimmerman, knocked him down and straddled him as alleged by Zimmerman but that the police had shown up and stopped the fight before it went any farther. First, Martin would have have been able to argue that he was standing his ground in response to an unprovoked assault by Zimmerman; and second, that if Zimmerman had been convicted of aggravated stalking (and his behavior definitely constituted the elements of that crime: 1) wilful 2) malicious 3) repeated following, and 4) making a nonverbal threat placing the target in reasonable fear for his safety), then simply by virtue of carrying a weapon during the commission of that crime, he would have been subject to a mandatory minimum sentence of 10 years (http://law.onecle.com/florida/crimes/775.087.html).

Second (and this is more abstract), whatever the contents of Martin's phone, they were not known to Zimmerman at the time of their interaction. So they could not have had any bearing on Zimmerman's assessment of Martin. In other words, it would make no logical to sense to say 'Z was afraid of M because M was the sort of person who talked about fighting and trading firearms' - you're inviting the jury to consider knowledge after the fact as an input to Zimmerman's self-defense claim.

Now it might seem like the prosecution is doing that with regard to Zimmerman's past history of studying criminal justice and so on - but that's part of the prosecution's job in terms of demonstrating motive and prior knowledge. The prosecution is not attributing such insight to Martin, who knew only that he was being followed by a stranger in a vehicle. There's no requirement for the prosecution in a homicide case to limit itself to the information that was available to the victim at the time of the incident (otherwise you'd be able to get away with murder as long as the victim were surprised).