“Yes. You said a medical examiner did an autopsy on this girl’s body?”
“Yes. The state medical examiner in Kentucky. The body of the girl—Leatha Rutherford was her name—was found hidden in a trash pile outside Lexington.”
“Why didn’t the medical examiner see the stab wound?”
“Good question. By the time she was found, she’d been dead nearly six months, so there just wasn’t enough soft tissue left to show the traces of a stab wound. The M.E. also took X-rays, but because the first rib runs underneath the clavicle”—I tapped my chest again—“the knife mark was masked on the X-rays.”
“And how did you happen to find it?”
“Dumb luck,” I said, earning a few laughs. “Actually, I have to give maternal doggedness the credit for this. Leatha was eighteen when she disappeared. The M.E. ruled her death a homicide, but he listed the actual cause of death as ‘unknown.’ She was buried, and the case more or less came to a dead end, but her mother wouldn’t give up. She kept nagging the detectives, and then she contacted me. She’d seen me on a television show—60 Minutes? no, wait, it was48 Hours, I think—and she sent me a letter. ‘If anyone can figure out how Leatha died, it’s you,’ she wrote. ‘Please help me.’ How do you say no to something like that? So I took a graduate student up to Kentucky, and we exhumed the bones. We brought them back to the morgue in Lexington, cleaned off the remaining tissue, and we got lucky. If dogs had gotten to the bones or if the knife had passed cleanly between the ribs instead of nicking this one, we would never have known what killed her.”
The red laser dot twitched and skittered along the cut mark again.No wonder cats love these things, I thought. “That nick in the bone is about half an inch long, an eighth inch wide, and a quarter inch deep,” I said, “but here’s how it looks up really, really close.” I flicked to the next slide. “We wondered if we could learn anything more about the murder by examining the cut mark more closely, so we took the rib back to UT and looked at it under a scanning electron microscope.” At this scale, magnified hundreds of times, the edges of the rib could not be seen; instead an area measuring less than one inch square filled the Smithsonian’s twenty-foot screen. The surface of the outer, cortical bone—ivory smooth to the naked eye and to probing fingertips—appeared ragged and spongy, like bread dough allowed to rise for too long. The small notch was now an immense fissure, wider than the span of my arms. I outlined it with the pointer. “Look carefully at the cut mark,” I said. “What do you see?”
“There’s a chunk of something down in the cut,” a man near the front called out quickly. This fifty-dollar-a-head crowd was quick and competitive, like a bunch of straight-A students competing in Brain Bowl.
“Very good,” I said. Lodged deep in the fissure was what appeared to be a boulder, several times the size of my head. “That looks pretty big under the electron microscope, but it’s actually a tiny speck, about a thousandth of an inch in diameter. About the thickness of the down on a newborn baby’s head. We analyzed that speck with an attachment to the microscope, something called an atom probe. Anybody want to guess what that speck is?”
Comments popped like kernels of corn. “Blood.” “DNA.” “Semen?” “Ooh, gross.” “Blood.” “Steel.”
“Steel’s close,” I said, “but not quite right. That’s a particle of cerium oxide. Cerium oxide is a ceramic that’s used to make knife sharpeners. The man who stabbed this girl had just sharpened his knife.”
A woman exclaimed, “Oh, dear God.”
The man near the front said, “So they did catch the killer?”
I always hated answering this question. “Unfortunately, no. If this were an episode ofCSI, they would have arrested him after fifty-nine minutes. But in real life, people get away with murder. The police thought she’d been killed by one of her relatives, an uncle; the rumor was, he had a big pot patch and Leatha had threatened to tell the police about it. Her body was found in the woods near his house, hidden in a trash heap.” I always had trouble telling the next part. “The police actually found a cerium knife sharpener in his kitchen drawer.” I heard murmurs of distress and indignation from the audience.
“But there was no direct evidence tying him to the crime. ‘A lot of people have cerium knife sharpeners,’