There may be reason for the defense to pursue it, since the prosecution seems to be channeling DU, and DU has become obsessed about the prescription drugs Zimmerman was taking for his digestive disease.
It's common for a coroner to request a basic drug screen for a substance the deceased is known to have been using, and a more detailed broad drug screen too. The latter usually takes longer. The evidence disclosed so far had a THC test, but I didn't see a complete drug panel. Could be it just hasn't arrived yet, but if it hasn't been ordered, the coroner has retained material that could be used.
Bottom line, even if its well founded, it doesn't answer the question of whether Zimmerman feared death or serious injury, and that's the only relevant issue.
Amen.
In no way is it mere “conjecture” as to whether or not Trayvon was experiencing drug related effects at the time. You might look up the posts from a few days ago linking to the convenience store video from shortly before the incident.
It is purely a question of “what”, not “whether”.