Common Misconceptions

Several erroneous ``explanations'' of various features in the March 19 incident appeared in the press after the incident. These ``explanations'' came from prominent physicians, anonymous law enforcement officials, politicians, and media personalities. We take this opportunity to clarify these misconceptions:

(1)

Fallacy.  A bullet with high temperature will burn the clothing and the skin on contact.

Fact.  As explained in §3 and §4, the surface temperature of the lead bullet was at most $200\tccentigrade$ when it impacted Chen's jacket. The contact time of the bullet with the jacket is approximately 0.1 millisecond, and the contact time of the bullet with any small piece of abdominal tissue is about 0.2 millisecond. That contact time is too short (by two orders of magnitude), insufficient for the relevant conductive thermal process between the bullet and the target to take place.

While a bullet itself does not burn skin or clothing, burn injury does happen in gunshot wound, but only when the barrel is in contact or near-contact with the skin. The primary reason of such thermal injury is the hot air or flame from the muzzle. See also the discussion in 3.7. In the situation of the March 19 incident, the muzzle was at least three meters away from President Chen; the ``hot zone'' according to the Lee Committee was much further away. Moreover, President Chen's abdomen was covered by an undershirt, a shirt and a jacket, seven layers of fabrics in all. In addition, no gunshot residue was found on Chen's jacket. So the scenario of burn injury in near-contact wound does not apply.

It is ironic that, during the first week, the presence of burn mark on Chen's abdomen was emphasized by Taiwanese government officials and Chen's supporters as a proof of Chen's innocence. They argued that the burn mark ``proves'' that Chen's wound was indeed caused by a gunshot; therefore, the March 19 shooting was not staged. Later, Chen's attending physicians cited the cauterization as a factor to explain why the amount of blood on Chen's clothing was much less than what is expected from a $11\ {\rm cm}\times 2\ {\rm cm}\times 1.2\ {\rm cm}$ wound on the abdomen. In fact, science tells the opposite: That the bullet could not possibly have caused any burn mark. If one accepts the presence of burn injury on Chen's wound, then one must conclude that the March 19 incident did not happen as purported.

(2)

Fallacy.  A high speed bullet can generate enough heat through friction to burn the skin.

Fact.  We refer to 3.5 and the references [DM], [SK], [MSW] cited therein. Notice that the author of [DM] is a forensic pathologist and a medical examiner, who wrote from experience. The total linear kinetic energy of a 3.89 g bullet at 200 m/sec is approximately 77.8 joules, or 18.6 calories. In other words, with 100% efficiency, this amount of heat can increase 1 ml of water by $18.6\tccentigrade$. Moreover the round-nosed lead bullet at 200 m/sec is an extremely poor burn instrument. It is a very inefficient heat generator to begin with. Most of the kinetic energy was expended on disturbing tissues and clothing; both have much bigger mass compared with the bullet. The heat generated by the bullet was not concentrated at the edge of the wound. So, although the deceleration of a bullet does generate some heat, it was not enough to cause burn injury.

(3)

Fallacy.  The spinning of the lead bullet generated a lot of heat and burned Chen's skin

Fact.  First of all, the angular velocity of the lead bullet was low when it hit President Chen. Page 30 of the Summary and Conclusions part of the Lee Report stated explicitly that

``Shot number two, the solid lead bullet, ...was also not spin stabilized, and perforated the President's garments while tumbling.''

The experts' consensus in wound ballistics is that the spinning helps to stabilize a bullet, but is insignificant in bullet's capacity to inflict injury. The spinning kinetic energy of fast spinning bullets from military rifles is less than 10% of the total kinetic energy of the bullet. See [SK, p. 128, p. 187] and [DM, p. 59, p. 85].

Another point is that, a bullet makes less than a complete revolution during its contact with the tissue. As an example, the twist length of a $5.56\times 45 mm$ NATO bullet, fired from a M-16A2, is 7 in, i.e. it makes a complete revolution in 7 in. It is a very fast spinning bullet, making 5,169 complete rotations in one second. However it makes less than one complete revolution when it travels 11 cm, the length of Chen's wound, which is less than 7 in. The heat generated by less than one complete turn of a bullet is extremely limited.

(4)

Fallacy.  So many factors, including the exact location of the shooter, the exact speed of the jeep, the distance between the weapon and the target, the exact angle of the trajectory, the type and amount of propellant and primer used, are still unknown. Therefore you cannot draw definitive conclusions from any experiment.

Fact.  First we address the question concerning the speed of the jeep. According to the principle of relativity, one can use any inertial coordinate system when applying Newton's laws of motion, without introducing any apparent force. We can reasonably assume that the jeep Chen stood on was traveling at an essentially constant speed--the acceleration was quite small. Using the inertia coordinate system centered on President Chen, we can simulate the trajectory of the lead bullet with a stationary target.

According to Newton's Laws, with the target, the bullet and the impact location fixed, the entire damage pattern is determined by the following physical parameters:

• the instantaneous velocity vector of the bullet on impact,

• the orientation of the bullet on impact,

• the instantaneous angular velocity of the bullet on impact,

• the temperature distribution of the bullet on impact.

Among these, the effects of angular velocity and the temperature distribution are small; they do not change the damage pattern. The crucial parameters are the impact velocity and orientation. The CIB's shooting experiment is also based on the same principle.

The laws of nature dictate that, there exists a range of impact parameters (combinations of velocity and orientation) that will reproduce the totality of the damage patterns. If such a range of impact parameters does not exist, then the 319 incident did not happen as purported.