Understanding and Recovering Firearms Evidence at Crime Scenes

Firearms-related cases often involve a wide range of evidence, from a single bullet fragment with rifling marks to numerous cartridges and firearms. Each piece of evidence can provide critical information to identify the type of firearm used and potentially the specific weapon involved in the crime. This article delves into the types and recovery methods of key evidence, such as gunshot residues and wadding materials, and the role of ballistic imaging in forensic science.

Firearms Evidence at a Crime Scene

At the crime scene, a variety of evidence related to firearms can be encountered. These include:

Bullets and Bullet Fragments: These are typically collected individually after proper documentation and photography, and submitted to the laboratory for analysis. Cartridge Cases: They are found and collected in much the same way as bullets. Shotshell Wads and Pellets: These materials can indicate the gauge of a shotgun. They are gathered and preserved in a similar manner to bullets and cartridge cases.

By examining wadding materials, the examiner can determine the gauge of the shotgun, the manufacturer, and a range of possible shot sizes based on impressions in the shotshell wad. In some cases, individual characteristics can also be identified.

Gunshot Residues

Gunshot residues are another significant form of evidence. They are categorized into two main types:

Collection from the Shooter’s Hands: This involves the use of a collection kit to gather residues from the suspected shooter's hands. The primary purpose is to determine if a person has recently handled or fired a weapon. However, since this method does not identify the specific firearm used or the exact time of the incident, its value is limited. Consequently, many laboratories have stopped performing these examinations. Residues on Victims’ Clothing: This type of evidence is used to determine the muzzle-to-target distance. Often, this evidence is not visible to the naked eye and requires microscopic examination and chemical testing to develop.

It is crucial to handle the victim’s clothing with care, air-dry it, and store it in paper containers to maintain the integrity of the evidence.

Ballistic Imaging: Enhancing Forensic Technology

Ballistic imaging is a significant tool in forensic firearms identification. This technology involves assessing computer-based images of crime-related cartridge cases and bullets. The purpose is to evaluate the current law enforcement database and recommend ways to enhance its usefulness in providing leads for criminal investigations.

A book on this subject highlights that while maintaining a national reference database of images from all newly manufactured or imported firearms in the United States could seem beneficial, it is not advisable due to potential ethical and practical issues. Instead, the book suggests further research on an alternative method for generating an investigative lead, which involves tracing the location where a gun was first sold.

Evidentiary Recovery Methods

Recovering firearms evidence involves several methods and areas. Crime scene investigators may find firearms themselves at shooting scenes and send them to the laboratory for further analysis. Bullets, bullet fragments, cartridge cases, shotshell wadding, and other materials are collected individually and submitted to the laboratory for detailed examination.

Bullets that do not strike a person are often found embedded in nearby surfaces such as wood or drywall. In these cases, it is best to cut out a section of the material and submit it to the laboratory for examination. This approach prevents any marking from being altered or lost, thereby maintaining the critical information needed for identification and matching.

Conclusion

Firearms evidence, from gunshot residues to wadding materials, plays a crucial role in solving firearms-related crimes. Understanding the recovery methods and the significance of each piece of evidence can significantly aid in the investigation and prosecution of such cases. As technology continues to advance, tools like ballistic imaging further enhance the capabilities of forensic scientists in identifying and linking firearms to crimes.