The defense team will seize on this information and argue, whether fairly or not, that the pot somehow impaired Trayvon and made him more aggressive, or something.
It's the kind of information that is likely to help generate reasonable doubt in the minds of the jurors...
It matters to motive too. GZ on the phone to the dispatcher mentioned the guy he was watching looked high by the way he was walking around I guess. It matters because the prosecution is trying to say GZ “profiled” Martin solely on race when in reality it was Martin’s odd ( odd according to GZ) behavior that night, along with not recognizing him as a resident that got GZ’s attention. Now that we have confirmation Martin was indeed high, GZ is looking more and more authentic with his initial concern, and less like a racist profiler, no?