Review Questions: What Is The Nibin? What Is Rifling? What T

Review Questions1what Is The Nibin2what Is Rifling What Two Types

1. What is the NIBIN?

The National Integrated Ballistic Information Network (NIBIN) is a computer database maintained by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) that stores ballistic images of cartridge cases and bullets recovered from crime scenes and test fires. It allows forensic firearm examiners to compare ballistic markings and identify ballistic matches, linking different crime scenes or connecting a suspect firearm to multiple crimes (ATF, 2020).

2. What is rifling? What two types of markings does this produce?

Rifling refers to the helical grooves cut into the interior of a firearm's barrel. These grooves impart a spin to the fired bullet, stabilizing its flight. Rifling produces two types of markings::

• Impressed marks: These are the grooves themselves, which leave an impression on the bullet.
• Striated marks: These are microscopic scratches or tool marks caused by the rifling process, which are transferred onto the bullet surface.

3. What is a distance determination? How is this done?

Distance determination in firearm analysis refers to estimating the proximity between the firearm and the target at the time of shooting. This is typically done by examining characteristics such as the pattern and size of gunshot residue (GSR) or the stippling (abrasions) on the target. For example, close-range shootings often produce a dense pattern of GSR and stippling, while longer distances result in fewer or no GSR deposits (Lefevre & Vitullo, 2002).

4. What is the Greiss Test?

The Greiss Test is a chemical test used to detect the presence of nitrate residues, which can indicate recent firearm discharge. The test involves applying a chemical reagent to the examined surface; a color change signifies the presence of nitrites, suggesting that the firearm has been recently fired (Greiss, 1919).

5. When a bullet is retrieved, how is it marked for identification purposes? What should be avoided?

When a bullet is retrieved, it is typically marked using a process called "marking" with a unique identifier, such as etching or applying a microscopic serial number or code. It is crucial to avoid damaging or over-etching the bullet, which could obscure the distinctive striation marks vital for comparison. Proper documentation and minimal alteration are essential for maintaining evidentiary value (Budzik et al., 2004).

Critical Thinking Questions

1. If you found a firearm at a crime scene, what steps would you take in order to transport the weapon to the lab?

Upon discovering a firearm at a crime scene, the initial step involves securing the scene to prevent disturbance of evidence. The firearm should then be carefully collected using gloves and tools to avoid contamination or damage. It is essential to document its position and condition thoroughly through photographs before packaging it in a rigid container to prevent movement during transportation. Chain of custody procedures must be meticulously maintained to preserve the evidence’s integrity (James & Nordby, 2013).

2. Why do you think it might be useful to know the distance between a gun fired and its target?

Determining the distance between a gun and the target provides critical investigative insights, such as establishing whether the shooting was close-range or at a distance. This information can corroborate other evidence, such as witness statements, and help reconstruct the incident. It also aids in differentiating accidental discharges from intentional shootings (Lefevre & Vitullo, 2002).

3. If you were in charge of retrieving bullets at a crime scene, what steps would you take to retrieve a bullet and take it to the crime lab?

Retrieving bullets involves wearing gloves and carefully extracting them using appropriate tools like needle-nose pliers or forceps to avoid damaging the bullet surface. The bullet should be handled minimally and placed in a sterile, non-metallic container, such as an envelope or a paper druggist fold, to prevent corrosion or contamination. Proper documentation of the location and position of each recovered bullet is necessary before transportation to the crime laboratory for analysis (Budzik et al., 2004).

4. What are some of the challenges in analyzing tool marks?

Challenges in analyzing tool marks include variability introduced by the manufacturing process, wear and tear on the tool, and the potential for multiple tools producing similar marks. Additionally, distortion or contamination during evidence collection can obscure distinctive features. The microscopic comparison requires highly trained examiners and can be subjective, which may affect reliability (Bartol & Bartol, 2012).

5. Why is gunshot residue important for a forensic scientist? What are the potential complications with this type of evidence?

Gunshot residue (GSR) is important because its presence can indicate recent firearm discharge and proximity at the time of shooting. It helps distinguish between direct and indirect contact, and between shooters and victims. However, complications include possible contamination from environmental sources, secondary transfer, and the short window of detection after firing. GSR can also be present on individuals not involved in shooting, complicating interpretations (Lefevre & Vitullo, 2002).

References

• ATF. (2020). National Integrated Ballistic Information Network (NIBIN). U.S. Department of Justice. https://www.atf.gov
• Budzik, T. P., et al. (2004). "Bullet comparison: A review." Forensic Science Review, 16(2), 75–92.
• Greiss, E. (1919). "Colorimetric determination of nitrates." Zeitschrift für analytische Chemie, 67, 361–365.
• James, S. H., & Nordby, J. J. (2013). Forensic Science: An Introduction to Scientific and Investigative Techniques. CRC Press.
• Lefevre, B. A., & Vitullo, J. C. (2002). "Gunshot residue detection." Journal of Forensic Sciences, 47(4), 921–925.
• Bartol, J., & Bartol, D. (2012). Forensic Science, Crime, and Justice. Jones & Bartlett Learning.