Ballistics

Firearms evidence and identification has become a crucial part in investigation and solving crimes. It has led to thousands of successful investigations that otherwise would not have been. You see it in the news and on TV shows like CSI. Although CSI is far from true forensic science, the concept is still there. What is firearms evidence? How is it examined? This paper will look at the history of firearms identification and examine the two previous questions.

To talk about firearms identification we must first understand where it comes from. We must learn about the history. With the more and more crimes being committed with firearms there was obviously a need for the development of firearms identification in criminalistics. The first murder solved using ballistics was successful in 1835. Henry Goddard examined a bullet and found a very distinctive mark on it that was from the mold that made it. This led him to the discovery of the suspect because the matching gauge was found on his mold (Swanson16-17). " Calvin Goddard a U.S. physician who had served in the army during World War I, is the person considered most responsible for raising firearms identification to a science and for perfecting the bullet-comparison microscope (Swanson 17)." But there also were several other very important contributors including Charles Waite. Waite and Goddard worked together on firearms identification. There was one major contribution from Waite and that was the country's first catalog of firearms.

"Firearms identification is a discipline of Forensic Science that has as its primary concern to determine if a bullet, cartridge case, or other ammunition component was fired from a specific firearm (Muth 241)." Firearm evidence and identification evidence is usually needed in solving crimes such as murder, robbery, and suicide cases. When at the scene of these crimes the evidence is collected and then submitted to the firearms section of a police lab. This evidence usually includes firearms, fired bullets, spent cartridge cases, shot pellets and slugs, shell cases, gunshot residues, shot wadding, clips or magazines, firing-pin impressions, and extractor and ejector marks. The most common examination for firearms examiners are determining whether a certain bullet was fired from a weapon (Swanson 126; Muth 241). When examining bullets in a case there are two main ways investigators examine bullets; they either use lead analysis or ballistics.

Lead analysis is where examiners will compare the composition of metals like lead in the bullets. " The FBI Laboratory uses an ICP-AES protocol to determine the concentrations of seven elements, arsenic, antimony, bismuth, cadmium, copper, silver, and tin in lead specimens (Koons)." Lead analysis has been used by investigators and has been accepted in court cases, but there is a lot of question on its reliability. The big question is because the lead differs not only from the manufacturers but will vary among the batches of lead a company uses on its bullets. Many companies get scrap lead to use so there are many combinations of these elements.

Ballistics is the matching of bullets to guns and relies on marks left on the bullet or case (Boyce 60). The first step in looking at ballistics evidence is looking for similarities in what are called class characteristics. "Class characteristics are those that would be common to a particular group0 or characteristics that were designed into the make-up of a group of items (Muth 242)." These characteristics include the caliber and the rifling pattern of the weapon. The caliber of a bullet is its diameter in hundredths of an inch. For example a 38 caliber is 38 hundredths (.38) of an inch in diameter (Muth 242; Swanson 126). With each caliber though there are many variations. The bullets may differ in length, weight, and appearance. These differences will determine the cartridge each bullet will have. Some of the cartridges in the 22 caliber "family" include the 22 Blank, 22 Short, 22 Long, 22 Magnum and many others (Muth 242). Caliber is not to be confused with the bore of a weapon. Bore is the diameter of the barrel's interior between its opposing high sides or lands. This is better explained when talking about rifling.

Most handguns, rifles, and some shotguns have rifled barrels. Rifling is the cut groves down a barrel in a spiral. When a bullet is fired down a barrel it expands and follows these grooves giving it rotation usually in a right hand direction. Bullets need this spinning in order to be accurate; it is much like when you are throwing a football. These grooves leave marks on the bullets in a pattern. Each maker of firearms has different number of grooves in there barrel, some have 6 grooves and some have 8. "Typical rifling patterns are 4/right, 5/right, 6/right, 6/left, 8/right, 10/right, 16/right, and 22/right (Muth 245)." There are also differences in the space in between these grooves. The diameters of the land and groove impressions are measured in thousandths of an inch. Investigators will look at these patterns and try to match bullets. They will be able sometimes determine what make the gun is or match bullets to the murder weapon. This is important information when solving cases. They may be able to link cases together or clear some.

Many times in crimes there is never a firearm that gets recovered. This is where the class characteristics come into play. As said previously, when a bullet gets fired it picks up striations from the land and grooves down the barrel. These markings on the bullets can be examined and then can be used to gather a list of possible guns that may matching patterns in their rifling in the barrel. The examiner will use the caliber , the rifling pattern, and the diameters of the individual lands and grooves to search through a database of rifling parameters. The database that they search is controlled and provided by the FBI. They have been keeping records of guns for over 20 years and it is updated annually (Muth 246). Muth uses an example to show the results of a search. These searches are done with +/-.005 parameter. The table will show the results of a possible search for a 9mm Luger bullet with striations from a 6/right barel, land width of .055 and a groove width of .125 (Muth 246).

Cartridge Manufacturer Twist L&G Land Groove

9MM Luger AA Arms Inc. R 6 .055 .120

9MM Luger Astra R 6 .053 .128

9MM Luger Beretta R 6 .055 .130

9MM Luger Hi-Point Firearms R 6 .055 .120

9MM Luger Interdynamic R 6 .055 .124

9MM Luger Llama R 6 .054 .120