Free Skull Duggery by Aaron Elkins

enter the fifth intercostal space about an inch to the left of the edge of the sternum, possibly clipping one of the two bordering ribs, the fifth or the sixth. Whichever, it would then necessarily plow into either the left ventricle of the heart, or that part of the right ventricle that extended to the left of the sternum. Either way, it wouldn’t have been good news for the heart. Or for Garcia. Death within a few seconds.
    But there was something about the wound, about the ribs, something that had him wondering… wondering…
    “Let’s go back to the table,” he murmured, returning there with Sandoval trailing behind. A quick survey of the body’s exterior confirmed Bustamente’s observation that there was no exit wound in the back wall of the thorax or along the sides. As Bustamente had said, if a bullet had entered Garcia’s body, it had never exited.
    If.
    Sandoval read something in Gideon’s face: doubt, uncertainty… His own worried expression lightened a little. “What? What is it? Is there something-”
    Gideon quieted him with a motion of his hand. “Give me just a second. I need to…”
    The words trailed away as his attention focused hard on the shattered rib cage, in particular on the broken, splintery fifth and sixth ribs. Then he straightened up and returned to the sink, where, for a long few moments, he stood looking down at the dry, brown chunk of hide; at that comma-shaped hole.
    Sandoval followed him. “What is it?” he pressed. “What have you found? What are you thinking?”
    “What I’m thinking,” Gideon said slowly, after a silence that practically had Sandoval ready to explode, “is that Dr. Bustamente may have been wrong.”
    Sandoval blinked. A tremor of hope ran over his face. “Wrong? You mean… he didn’t get murdered?”
    “No, I’m not ready to go that far yet, but you see, the thing is, bullets don’t come out of the holes they go in by.”
    “But Dr. Bustamente, he said-”
    “No, they just don’t. They can’t, not unless they haven’t quite penetrated the skin in the first place. But this hole goes clean through, you see?”
    The reason they couldn’t come out was that, while an entry wound itself might remain open, the track that a bullet made through the underlying soft tissue closed up after the slug’s passage. Of course it was hypothetically possible, Gideon supposed, that in a case like this, where the internal organs had all pretty much disappeared so that the bullet might have been rattling around an empty torso, that it had found its way back out through the entry hole while the body was bouncing along on the burro. But he had never heard of such a thing happening, and the possibility seemed too remote to consider seriously.
    Besides, he had a better hypothesis.
    It was too much for Sandoval to handle. “So… so… what does it mean? Where is the bullet? If it entered through this hole here and there is no other hole by which it came out, and it did not come out through the same hole, then… then…?”
    “Then we need another explanation, and mine is that this isn’t an entry wound at all; it’s an exit wound.”
    “But the, the abrasion collar…” He pointed at the abraded area around the hole. “Dr Bustamente, he said an abrasion collar-”
    “And he was right. An abrasion collar usually does denote an entry wound. The bullet’s rotation-”
    “Yes, yes, I know,” Sandoval said, hurrying things along with a rapid, rotating motion of his hand. “Dr. Bustamente explained very thoroughly. Very thoroughly.”
    “Okay, good, but, you see, there is a situation in which an exit wound can show an abrasion ring very similar to the one around an entrance wound, and that’s when the skin is pressed against something-a floor, a wall, the back of a chair, even clothing, something like a belt-when the bullet exits. The pressure keeps the wound from tearing wide open the way a typical exit wound would, and the abrasion comes, not from the bullet