@otg I enjoyed your egg demo video very much. The damage to the shells shows that the initial point of contact is where the worst, deepest damage occurs with other cracks spidering out. But JBR's fracture is not like that, so Why?
IMOO the 3-part comminuted-to-displaced-to-linear fracture is a result of the weapon used and its special properties. IMOO the weapon was a golf club - but it was the grip end that made contact with her skull, and the head of the golf club was held like a handle by the attacker. I also believe it was a wood (aka driver) club, perhaps a 3-wood.
I have a 3-wood here and the diameter at the grip end is 1-inch tapering down the shaft to 1/2-inch where the grip material ends, meeting your brilliant size information, and also your brilliant analysis that the weapon is a cylinder since a cylinder-contacts-sphere results in an elliptical. The leather or polymer grip material also meets the requirement that the weapon did not cause her scalp to split open. iirc the ME testified that he was shocked to find so much internal cranial damage because none was observed externally. The grip material acted as padding. Multiple golf clubs were readily available in the basement. We have tested this and a person up to 5'6" can easily swing a 3-wood golf club while holding the head, and crash the grip end into the back of a couch (approximating JBR, maybe bent forward hiding her face) in a low 8-foot ceiling room (idk the exact ceiling height in the R's basement, but it is low). This a surprising powerful weapon with a painful bruising impact on an adult leg with light effort for testing, and could be very damaging wielded by someone in a rage.
Some notes on different golf clubs: Some golf clubs like putters and irons have very stiff shafts. The woods, however, have very flexible shafts. The manufacture of a modern wood shaft usually involves three different metal alloys along the the length to create a precise desired degree of flexibilty. The motto is "Let the club do the work" and the novice mistake is trying to muscle or power hit the ball. A slow motion film of Tiger Woods during a tee shot would actually show the wood club shaft ever so slightly bent back in the air as it whirrs toward the ball with a final snap! or kick! before the CRACK! of contact with the ball. Another way to think of this is like a whip that snaps! in the air - the sound is created by energy transfer. A wood club held out horizontally, one hand on each end, can be slightly flexed.
IMOO this property of flexibility is important to understand the three phase fracture injury result. As I posted previously, IMOO the crushed, comminuted fracture on the back of her head is the initial contact point - and it looks a lot like
@otg 's egg demos. This is followed by a change of plane of impact for the elliptical displaced fracture, with the entirety of the 5-inch linear fracture only the result of fulcrum effect energy transfer moving forward, and no surface contact, due to the flexibility of the wood club shaft designed to do just that, maximize energy transfer.
IMOO any weapon that is too rigid, or too hard, or too heavy, (bats, sticks, pipes, rebar) would not be capable of such a large energy transfer type of fracture but would instead have created a more or larger, crushing, deep, direct impact injury.
Thanks for all your hard work on this,
@otg. I am trying to think of a miniature, flexible eggshell weapon... maybe a piece of wire coat hanger for that flexible whip effect.
