The old saying that "Ignorance is bliss" may be true in some instances, but it is certainly not so in a shooting incident. Ignorance of various aspects of physical evidence and their ramifications can lead to false assumptions and distort the truth.
Consider the following case, which the author reviewed in the early 1990s. A man was charged with intentionally shooting a 12-year-old girl in the head, killing her, during an altercation with a group of individuals at a housing project. The defendant admitted having fired several shots into the ground in an effort to keep the group at bay but was adamant that he had not fired intentionally at the girl.
The location of fired cartridge cases found at the scene seemed to contradict where the defendant claimed he was standing. This was based on the fact that most semiautomatic weapons eject fired cartridge cases rearward and to the right. The defendant was firing a Chinese SKS 7.62 x 39 semiautomatic rifle loaded with Chinese-manufactured ammunition, consisting of bullets with an inner steel post surrounded by a lead core and a steel outer jacket.
Other physical evidence, however, was consistent with the defendant's claim. There were some apparent bullet strike marks on the ground in front of where the young girl had fallen. In fact, a bullet was discovered in the ground at one of the marks. It was flattened on one side. Another bullet was recovered from the girl's head, and it too was flattened on one side. The bullet had entered the girl's forehead resulting in a large, irregular wound. Given the construction of the bullet (which in effect constituted armor-piercing ammunition) and the fact that the 7.62 x 39 rifle is a high-velocity weapon, it seemed very strange that the bullet did not pass completely through the girl's head. To someone with firearms knowledge this would suggest that the bullet had much less energy than what would be expected.
An additional "red flag" was the irregular shape of the entry wound in the girl's forehead. Bullets produce holes that are either round or oval
shaped, depending on whether the bullet strikes at a 90-degree angle or something significantly less, and trained firearms examiners are familiar with this fact. Irregular bullet holes and wounds are indicative of a bullet that has been destabilized as a result of striking something else first.
When a bullet strikes something and either passes through it or ricochets, it loses a great deal of its energy (something on the order of 40 percent is not uncommon). In this case the fact that the bullet failed to exit the girl's skull combined with the irregular entrance wound suggested that an intermediary target was involved. The flattened bullet recovered at autopsy, along with the bullet strike marks observed on the ground between the girl's location and the defendant's, provided still more evidence of something other than a straight-on shot.
By reconstructing the shooting using a tripod-mounted laser the examiner determined that the angle of ricochet required to strike the girl was of the order of six degrees. That angle is within the range that would be expected for a ricochet off hard ground. A little knowledge also cleared up the apparent conflict between the location of the fired cartridge cases and the reported position of the shooter: An SKS rifle ejects fired cartridge cases forward rather than back and to the right rear like most firearms. In other words, there was no real conflict.
This case is a good example of the importance of having a knowledgeable firearms examiner present at a crime scene. Without proper training and knowledge it is easy to be blissfully ignorant. But incorrect interpretation of a crime scene can have very serious consequences, as people's lives often hinge on the results of investigations. In this particular case the defendant ended up being charged with negligent homicide rather than first-degree murder.
control is the same. Criminals, on the other hand, are seldom picky about ammunition and frequently use more than one brand in the same weapon. Usually their only concern is to carry out the crime they are involved in. Besides, most shootings take place within a few feet, where small differences in load are unlikely to affect the deadliness of a shot.
Another area of shooting reconstruction for which the crime laboratory environment is required is the testing of firearms for proper functioning. An issue that frequently comes up is the possible accidental discharge of a weapon in a shooting incident. Investigators often hear the phrase "the gun went off." The only way to substantiate or refute the statement is through laboratory examination and testing.
There are three ways that firearms can be discharged: intentionally, unintentionally, and accidentally. Intentional discharge is self-explanatory: Someone pulls the trigger on purpose. Unintentional discharge results from something other than a mechanical malfunction. Accidental discharge results from a mechanical malfunction.
The difference between unintentional discharge and accidental discharge can be nebulous. Things like a sympathetic nervous response or a reaction to surprise can result in the unintentional discharge of firearms, but these matters are beyond the scope of a crime laboratory examination.
Mechanical function or malfunction, however, is ascertained through laboratory examination and testing of firearms. The following are the typical questions associated with this type of testing:
• Will the gun fire upon being dropped?
• Will the gun fire upon the bolt closing?
• Will the gun fire fully automatic?
• Will the gun fire as a result of the slide (part of the action on a semi-automatic) being released without pulling the trigger?
• Will the gun fire as a result of the hammer being pulled back partially and then released?
The term hair trigger refers to an excessively light trigger pull. Trigger pull is the amount of force required on the trigger in order to fire a weapon. Depending on weapon types and designs, trigger pulls between four and 14 pounds are considered normal. Trigger pulls between two and four pounds are considered light. Trigger pulls below two pounds, and particularly below one pound, are referred to as "hair triggers."
The lighter the trigger pull, the more prone a weapon is to unintentional firing. This is why police agencies typically require their service weapons to have at least eight-pound trigger pulls. The NYPD takes this a step further by requiring their weapons have 12-pound trigger pulls.
It is not uncommon for individuals who are unfamiliar with firearms to claim "the gun just went off by itself." Firearms examiners and others with some knowledge of firearms recognize the impossibility of such an event, but it is true that broken or worn internal parts can make firearms unreliable and dangerous. A "backyard gunsmith" who attempts to improve the gun's action or to convert semiautomatic weapons to fire fully automatic can cause the same result. The determination of these conditions requires disassembly in the laboratory by a trained firearms examiner.
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