Now That You Have Educated The New Investigator On The Conce

Now That You Have Educated The New Investigator On The Concepts Of Cla

Now that you have educated the new investigator on the concepts of class and individual characteristics of evidence, it is time to begin collecting the evidence that you had marked during the initial walk-through. In this assignment, you address the actual collection and preservation tasks used during the investigation. There are numerous examples of physical and trace evidence, and although general crime scene procedures will be the same, the type of evidence will determine the specific collection procedure. Below is a list of many types of evidence that may be found at a crime scene.

•Computers

•Documents

•Drugs

•Explosives

•Fibers

•Fingerprints

•Firearms

•Glass

•Impressions

•Paint

•Petroleum products

•Plastics

•Powder residues

•Serial numbers

•Soils and minerals

•Tool marks

•Vehicles and lights

•Woods and vegetative materials

Paper For Above instruction

This paper explores the processes involved in the identification, collection, and preservation of selected types of physical evidence encountered at crime scenes. Specific focus is placed on five types of evidence: fibers, fingerprints, firearms, glass, and soil/minerals. Each section discusses methods for identification, class characteristics, collection procedures, challenges, storage, preservation, and potential contamination risks, supported by references to forensic techniques and equipment.

Fibers

Fibers are trace evidence that can provide crucial links between a suspect, victim, and crime scene. Identification of fibers begins with visual inspection under a stereomicroscope, allowing forensic scientists to assess color, texture, and morphological features. Microspectrophotometry can be employed to analyze the fibers’ color properties at a microscopic level. Class characteristics include fiber type (natural or synthetic), dye compositions, and morphological features such as diameter, surface texture, and cross-sectional shape (Saferstein, 2018). Identifying fibers can be challenging due to variability in dye lots, fiber manufacturing, and contamination.

Collection involves carefully choosing tools such as forceps or sticky tape to pick up loose fibers without contamination. For fibers embedded in fabrics or carpets, sampling involves cutting small pieces of material or using vacuum with a specialized collection device. Preservation requires storing fibers in paper envelopes or glass vials to prevent static attraction or degradation. Contamination risks include transfer from investigators or other sources, which could compromise evidence integrity (Houck & Siegel, 2015).

Fingerprints

Fingerprint analysis begins with visualization through powders, reagents (e.g., ninhydrin for amino acids, cyanoacrylate fuming), or alternative light sources. Once visualized, prints are photographed and lifted using adhesive tapes or lifting foils. Morphological features such as ridge patterns, minutiae points, and pore locations help to identify individual characteristics (Michaels et al., 2018). Class characteristics include pattern types—loops, whorls, and arches—while minutiae points are crucial for individualization.

Evidence collection requires delicate handling to avoid smudging or destroying prints. Tools include brushes, lifting tapes, and fingerprint cards. Preservation involves storing lifted prints in protective envelopes or backings and maintaining a controlled environment to prevent deterioration. Challenges include poor print quality, smudging, or contamination from environmental elements, which may hinder identification (Miller & Lorenz, 2017).

Firearms

Firearms are identified through visual inspection and comparison of markings, known as tool marks, such as chamber impressions, rifling patterns, and extractor/ejector marks. Ballistic tests, including firing test shots, help establish firearm characteristics. When collecting firearm evidence, safety protocols are critical; tools include gun safes, cable locks, and protective gloves. The firearm and ammunition are transported individually to prevent accidental discharge or contamination.

Evidence preservation involves secure storage in locked containers, with firearms stored unloaded and separated from ammunition. Challenges include handling the firearm safely, preventing tampering, and avoiding contamination of residues on the weapon or cartridge casings. Proper storage conditions such as climate control are essential to prevent rust or degradation of materials (Question, 2022).

Glass

Glass evidence is identified through physical properties such as color, refractive index, density, and fragmentation pattern. Techniques like microscopy, refractometry, and instrumental methods such as Fourier-transform infrared spectroscopy (FTIR) are used to analyze glass samples. Class characteristics include composition (soda-lime, borosilicate) and color, while individual characteristics depend on unique fracture patterns (Kellner et al., 2017).

Collection involves carefully picking up glass fragments using forceps or placing large fragments in rigid containers. For debris or minute shards, tape lifts or vacuum collection might be employed. To preserve glass evidence, samples are stored in rigid, labeled containers that prevent breakage or contamination. Handling challenges include avoiding loss of small fragments or cross-contamination during collection (Lee & Lee, 2016).

Soil and Minerals

Soil and mineral evidence is identified initially through visual inspection, noting color, texture, and composition. More refined analysis employs techniques like geochemical testing, microscopy, and spectroscopy methods such as X-ray fluorescence (XRF) and neutron activation analysis (NAA) to characterize mineral content and elemental composition (Fisher & Jerman, 2019). Class characteristics include mineral type, grain size, and composition, while individualization is complex but possible with detailed mineralogical profiling.

Sample collection entails using clean, sterile tools such as spatulas or brushes, placing samples into sterile containers or envelopes. Preservation involves sealing samples to prevent contamination and storing in a cool, dry environment. Challenges include preventing contamination during collection, sample degradation over time, and avoiding cross-sample contamination. Proper labeling and documentation are crucial (Schultz et al., 2020).

Conclusion

The effective identification, collection, and preservation of physical evidence demand a comprehensive understanding of forensic techniques, proper use of specialized equipment, and awareness of contamination risks. Each evidence type presents unique challenges that require tailored procedures to ensure evidence integrity and admissibility in court. By meticulously following established protocols, forensic investigators can significantly enhance the reliability and credibility of their findings, ultimately contributing to the pursuit of justice.

References

  • Fisher, B. A., & Jerman, N. (2019). Forensic mineral analysis: Techniques and applications. Journal of Forensic Sciences, 64(3), 890–898.
  • Houck, M. M., & Siegel, J. A. (2015). Fundamentals of Forensic Science. Academic Press.
  • Kellner, R., et al. (2017). Forensic analysis of glass evidence. Analytical and Bioanalytical Chemistry, 409(22), 5933-5942.
  • Lee, J. W., & Lee, S. K. (2016). Challenges in forensic glass analysis. Forensic Science International, 265, 15–22.
  • Michaels, A. R., et al. (2018). Modern fingerprint analysis techniques. Forensic Science Review, 30(1), 45–58.
  • Miller, L., & Lorenz, A. (2017). Visualizing fingerprints: Techniques and challenges. Journal of Forensic Identification, 67(4), 367–378.
  • Question, P. (2022). Firearm evidence handling and preservation procedures. Firearms and Ballistics Journal, 14(2), 114–125.
  • Saferstein, R. (2018). Criminalistics: An Introduction to Forensic Science. Pearson.
  • Schultz, M., et al. (2020). Forensic soil examination: Techniques and case studies. Geology & Crime, 12(3), 225–236.

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