So the last stop of a zombie headshot enthusiast (with plenty of free time) must be forensics journals. It turns out there are three kinds of people who are keenly interested in the way gunshots can lead to “immediate incapacitation”: police accused over pulling the trigger too many times, military snipers and zombie genre nuts. In most zombie-scenarios a wounded zombie still poses a massive danger and ammunition is likely in short supply, so knowing what part of the brain needs to be destroyed to prompt an immediate shut-down is useful. In this, the 1995 study “Penetrating gunshots to the head and lack of immediate incapacitation” by German researcher B.L. Karger is required reading. as is “Forensic neuropathology: a practical review of the fundamentals” by Hideo Itabashi.
Karger lays down the basics (“immediate incapacitation is possible following cranio-cerebral gunshot wounds or wounds that disrupt the upper cervical spinal cord only”) and Itabashi backs the conclusions with specifics, and nauseating color photos. Itabashi says that immediate incapacitation is “very likely” in head shots by a rifle or shotgun at close range, or a handguns with calibers larger than 9mm. Nothing too surprising there, but the locations of the wounds is of interest to zombie hunters. Itabashi says that hitting the brain stem or severing the spinal column between the second and third thoracic vertebrae (in the neck) will produce an instant kill, which follows the canon of typical zombie scripts. But he also includes a third location in the brain as a place where damage results in immediate incapacitation—and it’s located frontal lobe. The primary motor cortex exists on both sides of the brain. It sends signals, via neurons, to the muscles of the body. Destroy this and you have harmless zombie.