IMO, the hair sticking up effect is because the large fragmented piece of skull at the rear of the JFK skull (as in the lateral X-ray ) was turned inward when the bullet entered at upper right rear (occipital parietal )
However, it’s very suspicious to me as to why there is no CLEAR definite location of and entrance hole,and only a photo of a gloved hand gripping some hair , and resorting to Ida Dox pencil drawing.
It’s the same with the photo showing an intact forehead with eyes open and sockets intact, in contrast to Z film frames indicating totally obliterated skull and Frontal X ray indicating missing frontal forehead skull