“If you look closely,” Cooper said, stroking the cracks delicately with a fingertip, “you will observe that the edges of the fractures are splintered, rather than snapped cleanly. This implies that, at the time of the injuries, the bone was flexible and moist, not dry and brittle. In other words, the fractures are not a post-mortem artifact; they were inflicted at or around the time of death. They were caused by several forceful blows—I would estimate at least three—from a flat surface, four inches wide or more, with no sharp edges or corners.”

I beat the urge to swallow; he would see it if I did. “Well,” I said. “I’m no pathologist either, but that looks to me like it could kill someone.”

“Ah,” Cooper said, smirking. “It could, but in this case, we cannot state with certainty that it did. Look here.”

He groped around at Rosie’s throat and fished out two fragile slips of bone. “This,” he said, fitting them neatly together into a horseshoe, “is the hyoid bone. It lies at the top of the throat, just beneath the jaw, supporting the tongue and protecting the airway. As you see, one of the greater horns has been completely severed. A fractured hyoid bone is associated, so near exclusively as to be diagnostic, with either motor vehicle accidents or manual strangulation.”

I said, “So, unless she was hit by an invisible car that somehow drove into a basement, someone choked the living shite out of her.”

“This,” Cooper informed me, waving Rosie’s hyoid bone in my direction, “is in many ways the most fascinating aspect of the case. As we noted previously, it appears that our victim was aged nineteen. In adolescents, it is rare to find the hyoid broken, due to the flexibility of the bone—and yet this fracture, like the others, is clearly perimortem. The only possible explanation is that she was strangled with extreme force, by an assailant with some physical strength.”

I said, “A man.”

“A man is a more likely candidate, but a strong woman in a state of intense emotion certainly cannot be ruled out. One theory seems most consistent with the full constellation of injuries: the attacker caught her by the throat and slammed her head repeatedly against a wall. The two opposing forces, from the wall’s impact and the attacker’s momentum, combined to fracture the hyoid and compress the airway.”

“And she suffocated.”

“Asphyxiated,” Cooper said, giving me a look. “So I believe. Detective Kennedy is in fact correct that the injuries to the head would have resulted in death in any case, due to intracranial hemorrhage and damage to the brain, but the process could have taken anything up to a few hours. Before that could occur, she was quite probably dead of hypoxia caused either by manual strangulation itself, by vagal inhibition due to manual strangulation, or by obstruction of the airway due to the fractured hyoid bone.”