Lincoln wanted to blame the murder completely on Norris, and to do so, he had to have some evidence that Metzker’s face was broken by something other than Armstrong’s fist or slungshot. Enter Dr. Parker. Dr. Parker testified that the fracture to Metzker’s face could be a contrecoup fracture—something I had never heard of. I thought he was trying to blow smoke on the jury with some fast talk, and trying to transform a contrecoup brain injury into a fracture.
I’m now going to try to explain contrecoup brain injury, and it’s going to sound nothing like what you’d hear if a brain surgeon described it for you: The brain floats in a cavity filled with liquid. When something hits the head hard enough, the skull moves toward the brain and the brain hits the skull. The injury caused by the brain striking the skull where the blunt object hits it on the outside is called a coup trauma. Now, the brain acts like a rubber ball. It compresses, and then bounces across the skull cavity and hits the skull on the opposite side of the head. The injury caused when the brain hits the opposite side of the head is called a contrecoup trauma. You see a lot of that type of injury in severe child abuse cases and child murders. It seemed ridiculous to me to think that the brain would bounce across the skull cavity and hit the opposite side of the skull hard enough to cause a fracture.Researching this second book, I decided to dig deeper into the issue and was surprised to learn that there actually is an injury to the skull called a contrecoup fracture, and it happens in the fragile orbital bones around the eyes. Maybe Doctor Parker wasn’t blowing smoke after all. I dug deeper, and this is what I learned (once again, my description is NOT going to be given with medical precision): If a large enough area of the back of the head is hit hard enough, it won’t break, but the force of the blow will be transferred through the skull to the front where it will break the orbital bones. It’s kind of like the karate guy who lays five board one on top of the other, hits them, and breaks only the bottom board.
Doctor Parker’s explanation for Metzker’s facial fracture was less unlikely than I thought it was, but there were still some problems with it:1] The trauma to the back of the head has to cover a large enough area to keep the skull from breaking. If the skull breaks and caves into the braincase, the energy is dissipated in the back of the head and won’t transfer to the front. A neck yoke isn’t likely to cause a contrecoup fracture. Parker tried to remedy this by suggesting that Metzker could have fallen off his horse while riding home.
2] Contrecoup fractures are rare. Rare enough to call into question Doctor Parker’s testimony that he had treated three contrecoup fractures in his practice. An E.R. doctor in a large metropolitan area, maybe; a prairie doctor on a sparsely populated frontier, not likely.3] Contrecoup fractures are never compressed. It’s against the laws of physics. the force is going in one direction, the broken bones are not going to swim against the tide of the blow and penetrate the brain going in the other direction. In Metzker’s eye injury, the broken bones were driven into the skull; therefore the eye injury was not a contrecoup fracture.