Postmortem shows killing shot could not have been delivered from behind.
The two bullets that hit Brown's head both entered his head almost parallel to the plane of his face, with the killing shot going through the upper brow into his brain. So there is no way Brown was killed running away, not unless he had some form of physically-impossible running technique that included running with his head tilted right back. Brown was a football player, an athelete, so his running posture would be very orthodox. People running from being shot tend to hunch their shoulders and keep down, so the killing shot is impossible from behind. If his head had been turned to look over the shoulder then the shot that hit his eye socket would have traversed his face, but instead it travelled down his cheek and into his upper chest, and the shot that entered the top of his head would have smashed a trench across the top of his skull but not made a right-angled turn down into his brain.
If the killing shot was made whilst the officer was standing and Brown was on his knees at twenty-odd feet then the posture again doesn't fit, he would need to be kneeling and leaning forward with his chin tucked down into his chest to get close to the right angle. Some of the witnesses claim he was on his knees and had his hands and head up and was saying "don't shoot", in which case the shot would have entered the front of his head/face and travelled at a slight downward angle, almost horizontally. If the cop was six foot tall he would have been holding the gun at a level of roughly five-and-a-half feet, Brown on his knees would put his brow at four-and-a-half to five feet above the level street, so the shot would drop about a foot at most in twenty-plus feet - a relatively shallow angle. This did not happen, not with either headshot, the angle of penetration was almost parallel to the plane of his face. If Brown was on his knees and the cop walked up to close range and 'executed' Brown then the angle would be much steeper, but still not the almost vertical angle of the shots if Brown had his head up as claimed.
If the killing shot had been fired with Brown already face-down on the road, the so-called 'execution' claim, then the angle of the shots would actually penetrate the top of his head and travel forward in his head in relation to the plane of his face - this did not happen, both bullets that hit his head travelled at an angle slightly backwards from the plane of his face. If Brown was hit with both headshots when falling forward onto the ground then the two shots would have to have been fired in very rapid fire and at a distinctly different time to the shots that hit his right side and arm more horizontally, yet some of the witnesses claim the shots were all fired "pow-pow-pow-pow" when Brown was on his knees. Such 'witness' statements are beginning to look a bit unclear, being generous.
Rapid fire would fit with the idea the cop was being rushed, not with the more deliberate and aimed fire that a trained shooter (such as a cop) would use against a stationary target. Even if the cop was using double-taps there would be two 'pows' with a pause to adjust aim before the second set of shots - 'pow-pow....pow-pow' - and not the string of rapid shots.
But, if Brown had his shoulders hunched and head down and was rushing the cop in the manner of an American football forward, something Brown was accustomed to doing, then the impact angles are possible, and the rapid fire is more likely as the cop switches to trying to stop the attacker in the short space between them. Therefore it appears to me that the autopsy report adds more weight to the cop's side of the story than those of the 'witnesses'.
As to why an highschool graduate would be stupid enough to try rushing an armed cop, you have to ask why an highschool grad would be stupid enough to rough-up a store clerk and steal a box of cigars in front if a video camera, or attack a cop in his car, which suggests Brown may have been less than lucid. Obvious suggestions would be drink or drugs, both of which should show up on the full autopsy report in the bloodwork.
If posters wish to propose otherwise then please do so without relying on JFK-style 'magic bullets' that defy the rules of physics. The more 'Libertarian' might also want to ponder the idea that the Tasers they so hate might have stopped Brown without the need for lethal force.
Biting the hand that feeds IT
