There are two other problems with Posner's theory, as I explain in my article on the Tague wounding and in my chapter on the subject in A Comforting Lie.
One, Posner assumes that his tree-branch-collision bullet was fired between Z140 and Z166, since this is the timeframe in which five witnesses saw a bullet strike the pavement behind the limo. Now, before I continue, I should note that Posner deserves credit for at least acknowledging that a bullet did strike the pavement before Z166. Many WC apologists deny the pavement strike because they view it as too problematic for their version of the shooting, even though five witnesses saw it happen.
Anyway, to assume that an FMJ bullet fired from the sixth-floor window hit a branch of the intervening oak tree, we would have to believe that the supposed lone gunman completely missed, not only Kennedy, but the entire limousine, from an elevation of 60 feet and from a distance of less than 140 feet. Even the Warren Commission (WC), in a rare display of logic and common sense, admitted it was hard to believe the gunman would have been so severely off the mark with his first and closest shot:
On the other hand, the greatest cause for doubt that the first shot missed is the improbability that the same marksman who twice hit a moving target would be so inaccurate on the first and closest of his shots as to miss completely, not only the target, but the large automobile. (WCR, p. 111)
Two, in order for Posner's errant shot to have had any chance of fragmenting from hitting an oak tree limb, assuming for the sake of argument this is even possible, the missile would have had to strike far enough up the limb so the limb would not bend or snap when the bullet hit. This would have been a staggering, unbelievable miss if fired between Z140 and Z166 from the sixth-floor window. To hit a limb far enough up its structure during this timeframe, the limo, much less JFK, would not have even been in the gunman's field of aim when he pulled the trigger.
Furthermore, as mentioned in previous replies, a bullet that hit far enough up an oak limb that that the limb did not bend or snap would not have fragmented into several fragments but would have penetrated deep into the limb and would have remained substantially intact. Such a collision certainly would not have caused the copper jacket to separate from the lead core, but Posner must assume this happened because the smear taken from the curb scar contained no copper (WCR, p. 116).
Anyone can verify in sources on bullet behavior that an FMJ bullet will penetrate and not break apart when it hits oak wood. I asked Google AI what would happen if an FMJ bullet traveling at medium velocity hit a piece of oak wood. Google AI answered as follows, just as I knew it would:
When a medium-velocity FMJ (Full Metal Jacket) bullet strikes a piece of oak wood, it punches a deep, narrow hole through the dense grain while staying mostly intact.
Impact and Penetration
Deep entry: The bullet cuts cleanly into the wood instead of mushrooming or flattening out immediately.
Rapid deceleration: Oak is a hard, dense wood. It slows the bullet down much faster than soft pine or drywall.
Stopping power: If the oak board is thick (such as 4 to 6 inches), the bullet will likely lose all its energy and stop inside the wood. If the board is thin, the bullet will pass right through.
When I asked Google AI what would happen if an FMJ bullet traveling at low velocity hit a piece of oak wood, it once again answered just as I knew it would:
A low-velocity full metal jacket (FMJ) bullet will cleanly punch a round hole into oak wood and stop without breaking apart.
What Happens to the Bullet
Stays intact: The hard metal cover keeps the lead core from flattening.
No expansion: The bullet keeps its original shape because the slow speed is not enough to deform the metal.
Slows down fast: The heavy resistance of the wood quickly robs the bullet of its forward motion.
Keep in mind that FBI firearms expert Robert Frazier told the WC that the alleged murder weapon was a rather low-velocity rifle (3 H 414), while some experts, using a different velocity scale, say the 6.5 mm Mannlicher-Carcano rifle is a medium-velocity weapon. No one, but no one, says the rifle is a high-velocity weapon.
Posner obviously knew nothing about FMJ bullet behavior when he formulated his tree-branch-collision theory. He erroneously assumed that his supposed FMJ bullet would not only produce two large fragments but would shed its copper jacketing.
The WC's alternative explanation for the Tague wounding, aside from being hopelessly and intentionally vague, is even worse than its headshot-fragment theory: "or it might have been a product of the fragmentation of the missed shot upon hitting some other object in the area" (WCR, p. 117).
This is a lame, useless explanation. The WC claimed to have no idea where the alleged lone gunman's miss landed, rendering its "hitting some other object in the area" theory useless from the outset. The WC refused to acknowledge that a bullet dug into the grass near the manhole cover in the vicinity of the triple underpass (even though the strike was observed and reported by Officer J. W. Foster, and even though a photo of the hole in the grass was published the next day in the Fort Worth Star-Telegram). The WC also refused to acknowledge that a bullet hit the sidewalk on the north side of Elm Street (even though it dug a 4.0 x 0.5-inch scar into the sidewalk, and even though two witnesses saw the scar before it was crudely patched). Thus, it is not surprising that the WC did not even speculate about where the supposed single assassin's errant shot landed.
And, of course, the WC could only float its specious explanations by dismissing the fact that Tague insisted the second shot was the one that caused his wound. The WC clearly leaned toward a first-shot miss, not a second-shot miss, which is why it could not accept Tague's clear, reasonable testimony, even though Tague, like several other witnesses, specified that the first shot he heard sounded different than the others, and even though he specified he heard the third shot after he felt something sting his face (7 H 552-555).
Unless the supposed lone gunman was legally blind, if his alleged second shot missed, it would have landed in the limo's passenger compartment, or on the limo's trunk or hood, or on the right side of the limo. The same would have been true if the alleged single shooter's first shot missed. If the supposed sixth-floor "sharpshooter" somehow managed to miss the entire huge limousine with his first and closest shot, it would have landed on the street or sidewalk in the vicinity of the limo, well over 300 feet from the Tague curb scar and with at least five witnesses standing between the impact point and the Tague curb scar/Tague himself.
The fact that the lone-gunman theory simply cannot explain the Tague wounding is the reason that Specter and the FBI tried so hard to ignore it. It should be noted that Specter never asked the Commission's wound-ballistics experts about the WCR's bogus theory that a fragment from the head shot could have caused Tague's wounding. Those experts would have told him that such a fragment would have had to exit from the right side of the skull (whereas Tague was standing to the left of the limo), that it would have had to clear the limo's roll bar and windshield, and that it most certainly would not have had enough velocity to veer over the roll bar, then dive downward and leftward, and then travel over 200 feet and hit the curb hard enough to scar it or hit Tague's face hard enough to cut it.
