Review Questions: What Are The Four Types Of Evidence In A C

Review Questions1what Are The Four Types Of Evidence In A Criminal In

1. What are the four types of evidence in a criminal investigation?

2. What are individual characteristics? Give an example of an individual characteristic.

3. What is the difference between individual characteristics and class characteristics?

4. What are physical and chemical properties? Give an example of each.

5. What do forensic scientists do to collect and preserve soil samples?

Critical Thinking Questions

1. Why do you think forensic scientists are so careful that the tests they do are sensitive, reproducible, and specific? What might happen if they were less careful about this?

2. Which type of evidence do you think is most useful in an investigation? Why?

3. Why do you think that forensic scientists continue to look for class characteristics given their limitations?

4. What do you think would be some of the challenges in collecting and preserving impressions? Why?

5. If you were on a jury, do you think you would expect individual characteristics in the evidence? Why or why not? What effects might it have if individuals expect to have individuals characteristics presented?

Paper For Above instruction

In criminal investigations, evidence plays a pivotal role in establishing facts, linking suspects to crime scenes, and ultimately leading to convictions or exonerations. Understanding the types of evidence and their specific characteristics is essential for forensic scientists, law enforcement, and the judicial system. This paper explores the four primary types of evidence encountered in criminal investigations, the distinction between individual and class characteristics, and the importance of physical and chemical properties. Additionally, it discusses the meticulous procedures for collecting and preserving soil samples, the importance of test sensitivity and reproducibility, and the ongoing relevance of class characteristics despite their limitations. It concludes by examining the challenges of collecting impression evidence and the perspective of a juror regarding individual characteristics in evidence presentation.

The four main types of evidence in a criminal investigation are physical evidence, biological evidence, trace evidence, and impression evidence. Physical evidence includes tangible objects such as weapons, fingerprints, or clothing that can be directly associated with the crime scene or perpetrator. Biological evidence encompasses bodily fluids, hair, or tissue that can provide vital information about the suspect or victim. Trace evidence refers to small quantities of materials like fibers, gunshot residue, or soil — substances transferred during the commission of a crime. Impression evidence involves marks or patterns left by objects or substances, such as footprints, tool marks, or bite marks, which can be crucial for identification and comparison.

Within forensic science, the concepts of individual and class characteristics are fundamental. Individual characteristics are unique features that can distinctly identify a specific object or person. An example of an individual characteristic is a fingerprint ridge pattern or a DNA profile. Conversely, class characteristics are features shared by a group of objects or individuals and are not unique to a single source. For instance, the type of car paint or the caliber of a firearm cartridge are class characteristics, as they can narrow down suspects but cannot definitively identify a single source.

Physical properties describe the measurable or observable features of a substance, such as density, melting point, or color, which help in identifying and comparing materials. Chemical properties, on the other hand, involve the chemical behavior or reactivity of a substance, such as reactivity with acids or combustion characteristics. An example of a physical property is the melting point of glass, whereas the chemical property example could be the flammability of gasoline. These properties aid forensic scientists in analyzing evidence substances, ensuring accurate identification and comparison.

Collecting soil samples requires precision and care to prevent contamination and preserve their integrity. Forensic scientists use sterilized tools and containers to gather soil, documenting the location and context meticulously. They often perform on-site tests to determine the soil's composition and then take samples to the laboratory for further analysis. To preserve the sample, they store it in airtight containers, label it securely, and prevent exposure to environmental factors like moisture or heat that could alter its properties. Proper handling ensures that soil evidence remains reliable during laboratory examination and courtroom presentation.

In forensic science, the sensitivity, reproducibility, and specificity of tests are paramount. Sensitive tests can detect minute quantities of evidence, increasing the likelihood of successful detection. Reproducibility ensures that results can be consistently replicated across different tests or laboratories, reducing errors and enhancing credibility. Specificity confirms that tests target only the substance in question, avoiding false positives that could jeopardize case integrity. If forensic tests lack these qualities, it could lead to wrongful accusations, acquittals, or the misinterpretation of evidence, thereby undermining the justice system.

Among various types of evidence, biological evidence—such as blood, hair, or DNA—often proves most useful because it can be directly linked to individuals, providing strong identification and linkage to the crime scene. DNA analysis, in particular, offers a high degree of specificity and individualization, making it a powerful tool for investigators. While other evidence types, such as fingerprints or fiber analysis, are also valuable, biological evidence's ability to uniquely identify individuals makes it especially compelling in criminal prosecutions.

Despite the limitations of class characteristics, forensic scientists continue to search for them because they help narrow the scope of suspects or sources, guiding investigative efforts. Class characteristics are valuable as initial screening tools, especially when individual characteristics are absent or unobservable. For example, the type of shoe print or tire tread pattern can exclude many sources and focus the investigation on a particular class of objects, directing resource allocation more efficiently.

Collecting and preserving impression evidence, like footprints or tool marks, presents numerous challenges. Impressions can be easily distorted by environmental factors such as wind or rain, or compromised by mishandling during collection. Ensuring the impressions are documented thoroughly through photographs and casts before collection is critical. Additionally, impressions may wear away or be contaminated, making preservation difficult. Precise and careful techniques are necessary to maintain the integrity of these impressions for later analysis.

From a juror’s perspective, expecting to see clear individual characteristics in evidence could influence their perception of credibility. Evidence with identifiable individual features, such as DNA or unique fingerprints, can strengthen confidence in a conviction. Conversely, lack of such evidence might sow doubt, especially if class characteristics are relied upon alone. Therefore, jurors might expect forensic evidence to demonstrate individualization to ensure fairness and confidence in the legal process, although understanding the limitations of certain evidence types is equally important for a balanced judgment.

References

• Saferstein, R. (2018). Forensic Science: From the Crime Scene to the Crime Laboratory (4th ed.). Pearson.
• Baldwin, R. (2019). The Science of Forensic Evidence. CRC Press.
• Byrd, J. T., & Amenden, R. P. (Eds.). (2017). Scientific Crime Detection and Prevention. CRC Press.
• Gill, J. (2015). Practical Forensic Toxicology. CRC Press.
• James, S. H., & Nordby, J. J. (2019). Forensic Science: An Introduction (5th ed.). CRC Press.
• Houck, M. M., & Siegel, J. A. (2015). Fundamentals of Forensic Science. Academic Press.
• Hogarth, J. (2018). Principles of Forensic Chemical Analysis. Wiley.
• Semmler, J. S., & Tindall, J. (2020). Forensic Science: An Introduction. Jones & Bartlett Learning.
• Hopwood, L. E. (2021). Trace Evidence Examination. CRC Press.
• U.S. Department of Justice. (2019). Forensic Science Communications. National Institute of Justice.