Having read through the preceding posts I have to agree with
@75 on this. I am not a fan of neck shots but do use them (high neck) on occasion where that is all that is offered. My reasoning is this. With a neck shot the aim is to disrupt spinal cord function by breaking bone. There are 7 Cervical vertebrae denoted by C1-7, 13 Thoracic vertebrae that have attached ribs denoted by T1-13 and 7 Lumbar vertebrae denoted L1-7.
If you are disrupting the spinal cord then a shot affecting C1-C3 will be fatal as the muscles of respiration will be paralysed and motor function will be lost to all limbs. This equates to the high neck shot. If the spinal cord segments between C4 and T2 are destroyed then there will be immediate tetraplegia (all four limbs will be incapable of movement) but the brain will be fully functional until coup de grace or blood supply to the brain is lost by more peripheral tissue damage. Bear in mind that severing one carotid artery will not cause death as the vascular supply to the brain has a circular layout (circle of Willis) that maintains blood supply in this situation. A severe spinal injury behind T3 will only cause paraplegia (hind limb paralysis). So the so called low neck shot is likely to result in delayed loss of consciousness. Others have already eluded to the eyes following you when you approach the paralysed deer. This surely cannot be considered acceptable from a welfare perspective if another shot was available!
The next important factor is the lack of clear aiming point with neck shots, particularly low neck shots. This can easily result in wounding and failure to recover the deer. The spinal column does not always lie in the middle of the neck and if a shot fails to hit the bone of the spine in the neck it should be regarded as a failed shot. You may get away with it and anchor the deer but be completely honest with yourself that you have failed your task of hitting the spine and reflect on what could have gone wrong.
My preference is to take a hilar shot as first choice and a head or high neck shot as a second choice. It is rare that I cannot get one of these two shots to work. Occasionally in woodland I may find the head and heart/lung area obscured and will then consider a neck shot as a last resort. If there is any movement after the shot (other than legs kicking)?then another round will be sent immediately, even if that means poor shot placement and a spoiled carcass. Anything with a residual blink on approach gets a second shot or is bled.