The Abrasion Collar

Abrasion collars are indicative of entrance wounds from high velocity projectiles. The do not occur with exit wounds. They are caused by the impact of the bullet to the skin and the stretching that occurs. When this occurs, small amounts of sediment on the projectile may rub off when the bullet makes contact and contribute to the discoloring. Often, this residue can be wiped clean from the wound. It's presence is only indicative of an entrance wound. The wound on Kennedy's back had an apparent abrasion collar. This can be seen in an enhanced enlargement of the autopsy photograph. See below.

Without a doubt, an abrasion collar is significant for entry wounds. The wound on the back was one of entrance, not exit.

The only question surrounding this wound is why the wound terminated after a very short distance. The autopsists noted that the bullet track terminated after a distance of less than one inch. Why? The wound track is made when the bullet passes through. It goes through the skin, fascia and muscle in the position that the victim was in. Then, after a person is shot, they move. When they move, the muscles move. If the bullet transits more than just one muscle, the track can be obscured. If the victim dies and there is enough time for rigor mortis to set it, as with President Kennedy, and the affected muscles have moved, then the wound track can be obstructed by underlying muscle. Kennedy was shot in the upper back, or lower neck. It was at the junction of the cervical and thoracic areas. Several muscles traverse this area. Such muscles may include the levator scapula, rhomboid minor and the trapezius. In addition, many smaller muscles traverse that area of the upper back and lower neck. These could include the erector spinae musculature, splenius capitus, splenius cervicis and serratus posterior superior. This represents the major portion of possible muscles that could've been hit in the posterior back and neck junction.