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Firearms & Toolmarks
The Firearm and Toolmark Identification Unit of the Michigan State Police Forensic Science Division is comprised of forensic scientists and technicians, civilians, and enlisted members of the MSP. The members of this unit are responsible for a variety of examinations. The primary examination conducted is the comparison of toolmarks observed on fired components of ammunition, or other surfaces, to determine if they were produced by a particular firearm or tool. Other examinations include function testing of firearms for entry into the National Integrated Ballistic Information Network (NIBIN), serial number restoration, distance determination, and classification of fired bullets.
Agencies from across the state can submit firearm and toolmark related evidence to any of our laboratories in Michigan. Examinations completed in the Firearm and Toolmark Identification Unit can assist agencies with linking evidence to a specific firearm or tool. The examinations can also link evidence recovered at another scene that occurred on a different date and/or in a different city.
The Firearm and Toolmark Identification Unit conducts the following exams:
- Firearms comparisons and classifications
- Toolmark comparisons
- Distance determination
- Serial number restoration
- NIBIN Entry
- 3D technology
Firearms Comparisons and Classifications:
Individual toolmarks can be found on the barrel and breechface of a firearm, produced during the manufacturing process also from use and damage to the firearm. These toolmarks are imparted on components of ammunition when the firearm is fired. Fired components of ammunition (bullets, cartridge cases, shotshells) recovered from a crime scene and a firearm recovered from a person of interest can be submitted for comparison. Pristine test shots are obtained from the suspected firearm using a bullet recovery water tank. The test shots are compared to the evidence collected from the crime scene. Microscopic toolmarks imparted on components of ammunition are compared using a comparison microscope. When no firearm is recovered, the fired components of ammunition can be compared to each other and classified to determine how many firearms were used and a list of suspected firearms can be produced.
Fired Cartridge Case Comparison
The tool working surface of a hard object will impart striated or impressed toolmarks when it encounters a softer object. Objects found at a crime scene with observed toolmarks (pried open door, damaged safe, cut lock) or casts of the toolmarks along with the suspected tool from a person of interest can be submitted for comparison. Test marks are created with the suspected tool and compared microscopically to the submitted toolmarks using a comparison microscope. Examples of comparisons that can be completed are a knife to a stabbed tire, bolt cutters to a cut lock, diagonal cutters to cut wires, box cutter to a cut hose, axe to a damaged safe.
Toolmark Comparison on Copper Wire
Distance Determination (Gun Shot Residue):
When a cartridge is discharged from a firearm, gases, and burnt and unburnt powder particles exit the barrel with the bullet. These particles can create a pattern on the target surface (i.e., outer most garment of the victim’s clothing). This pattern may be visible to the naked eye and may have characteristics that can be enhanced through chemical processing. Based on the characteristics of the pattern, a potential distance between the muzzle of the firearm and victim can be determined. To determine the distance, test panels are shot in a controlled environment at predetermined distances with the suspected firearm and ammunition. The shot test panels and the victim’s clothing are processed chemically for nitrites and lead. The physical characteristics of the hole and the chemically treated patterns are compared to determine a potential muzzle to target distance.
Physical (L), Nitrite (C), and Lead (R) Patterns
Serial Number Restoration:
A serial number is a unique identifier consisting of numbers and letters that is applied to objects, such as firearms, cars, and bicycles, so that they can be identified. Serial numbers can be destroyed intentionally or unintentionally inhibiting an object from being traced. Various methods such as polishing, chemical etching, and magnetic particle inspection can be used to restore the serial number.
Serial Number Restoration
National Integrated Ballistic Information Network (NIBIN):
The National Integrated Ballistic Information Network (NIBIN) is a database of stored images of fired cartridge cases from crime scenes and test shots from firearms. All semiautomatic (or auto ejecting) firearms are entered into the NIBIN database, as well as evidence that is found at a crime scene.
After a fired cartridge case is entered into the NIBIN database, the images are searched against other evidence and test shots already in the database. A list of potential associations is generated, which is reviewed by a technician to determine if there are any cases that can be connected. If there is agreement in the toolmarks observed on the fired cartridge cases, a NIBIN Lead is sent to the investigating agencies to communicate information about the associated cases. A NIBIN lead is not a confirmed identification until the evidence is resubmitted for a firearms comparison.
IBIS BrassTrax used to make entries into the NIBIN database
The Michigan State Police Forensic Science Division is active in staying up-to-date on current technologies in the Firearm and Toolmark discipline. 3D technology has been developing in recent years for the discipline. High definition, 3D scans of fired components of ammunition can be used as another tool to complete comparisons. The technology is also able to assign confidence levels to the comparisons and conduct controlled and database searches.