Rocketing along the barrel of a gun, a bullet accelerates continuously, building the energy that becomes the basic source of its lethal doings. Just how fast it accelerates depends on muzzle velocity — a poky 855 feet per second from a .38, vs. 1,155 feet per second for a slug from a 9 mm semiautomatic. On impact, two cavities typically form in the body: a relatively thin, permanent cavity, as tissue is instantly pulverized; and a larger, temporary, oval-shaped one, as tissue is thrust away from the wound track. Cavity size depends on the bullet and its velocity: A .357 Magnum slug, traveling at 1,393 feet per second, forms a permanent cavity much larger than that formed by a .45 round, traveling at 869 feet per second. And, often, it does a great deal more damage.
The carnage does not stop in the cavity-forming stage. It's where the bullet goes afterward that spells the difference between recovery and obituary. "If I know the exact path that the bullet takes through the body, I can figure out what may or may not be injured," said Haut, a mild-mannered physician's son who grew up in the suburbs of Philadelphia.
If you get hit in the torso, for example, you'll most likely be in big trouble. The abdomen is packed with vital structures — the stomach, the liver and the intestines, as well as major blood vessels. (Nonelastic tissue, such as that found in the liver and the brain, tends to fare the worst.) The chest is another place you don't want to get plugged; if a bullet nicks your heart or aorta, you'll probably die at the scene.