The state put on an expert witness who testified, based on her observation of the picture of the back of GZ's head, that his injuries looked "minor" and required no stitches. Other witnesses (e.g., the booking officer) testified that although GZ's head wound was still actively bleeding at the station, he declined to go immediately to the hospital and at no point lost consciousness. However, the defense put on an expert witness (Di Maio) who testified (correctly; see, e.g., research showing that even subconcussive head injury can lead to CTE) that serious, permanent brain injury and even death can result from an impact to the head that results in no loss of consciousness or concussion or even any external marks. He testified that GZ's lacerations suggested at least six impacts and perhaps more that didn't leave marks, and he described cases in which people under those circumstances later dropped dead an criticized officers for not insisting that GZ go directly to a hospital (noting cases in which arrestees had died in holding cells under similar circumstances and the prisons had been found liable). As for your definition above, GZ did say, in different words (e.g., his head felt like it was exploding), that he was in "extreme physical pain" in his Hannity interview (I confess I can't recall for sure whetehr the prosecution introduced that part into evidence or edited it out). In short, if you believe his version of events, then GZ couldn't have known that the injuries he actually received wouldn't cause serious bodily injury or death. Much more importantly, the extent of GZ's actual received injuries is, as the defense put it, "gravy" under the law; the law requires a reasonable belief in future (imminent) serious bodily harm, so the fact that GZ only had a (probably) broken nose and lacerations to the back of his head that didn't require stitches or result in loss of consciousness -- even if GZ could have known that these would be medically benign -- isn't the end of the story. The state's own witness (the African American JAG officer who taught GZ criminal justice), in one of the most jaw-dropping moments in a trial full of them, testified to this point of law (without objection by the prosecution, oddly) and when asked by the defense whether someone is obligated to wait until they have actually experienced serious bodily injury or death before invoking their right to self defense, responded, "I wouldn't recommend that." GZ "testified" through his media interviews that TM said "you're going to die tonight MF"; that he called for help multiple times over 40 seconds as his head was being slammed against the concrete multiple times; and that he feared that he would lose consciousness and didn't know what would happen at that point. (The last claim about loss of consciousness is from the Hannity interview, and again, I can't recall whether it was introduced at trial instead of edited out; I paid no attention to this case prior to the trial (which I increasingly think gives me a different perspective on the verdict than many who consumed lots of pretrial media on the case but little of the actual trial) so I didn't see the interview at the time it originally aired, but the networks have been playing it during the trial, and I may have seen it in that context rather than in trial.) Another expert for the defense (Root, I think) testified that under the circumstances (taking GZ's story as true) he had "no other choice" but to use deadly force or continue to be subject to an assault that other witnesses testified could be lethal. - http://prawfsblawg.blogs.com/prawfsblawg/2013/07/zimmermans-not-guilty.html