You Are A Member Of A Forensic Team That Just Finished Gathe

You Are A Member Of A Forensic Team That Just Finished Gathering Sampl

You are a member of a forensic team that just finished gathering samples from a crime scene where someone is suspected of breaking into a house and possibly attacking a female victim. The victim was home alone when she heard a noise and investigated. A man was seen fleeing the neighborhood a few blocks away when police arrived and was arrested pending forensic analysis. The forensic team collected various evidence including broken glass, stains on carpet, furniture, clothing, and drinking glasses, which need to be transported to the laboratory for testing.

This discussion addresses the protocols for delivering evidence to the lab, the methods for testing specific body fluids (blood, semen, saliva) on each piece of evidence, what positive results indicate, and how these tests are similar and different, supported by APA references.

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Proper evidence collection, preservation, and transportation are vital in forensic investigations to ensure integrity and prevent contamination. In this scenario, evidence such as broken glass, stains on fabrics and furniture, and drinking glasses would be carefully packaged to avoid cross-contamination. For porous evidence like fabric and furniture, evidence should be dried and individually packaged in paper containers or置evidence bags to prevent mold growth and degradation. Non-porous evidence such as glass and drinking glasses should be rinsed with sterile water if necessary, then air-dried and placed in hard plastic containers that provide a seal and prevent breakage during transit (Hanson & Hamel, 2010). Chain of custody forms must accompany all evidence to document its handling from collection to analysis, ensuring a clear audit trail. Evidence should be transported under secure conditions to the forensic laboratory, where it is cataloged and stored appropriately until testing.

Testing for body fluids such as blood, semen, and saliva on different pieces of evidence involves specific biochemical and immunological procedures. The initial step often involves presumptive tests, which quickly indicate the possible presence of a substance. For blood, the Kastle-Meyer colorimetric test is commonly used. It employs phenolphthalein, which reacts with hemoglobin in blood to produce a visible pink color within seconds, indicating a positive result (Cowley & Evans, 2011). For semen detection, the acid phosphatase (AP) presumptive test, often through a color change reaction, is employed. The presence of acid phosphatase, an enzyme abundant in semen, turns a violet or purple color when exposed to specific reagents (Hanson & Hamel, 2010). For saliva, the Phadebas test uses a starch-iodine reaction whereby the enzyme amylase reacts with the reagent to produce a color change, indicating saliva presence (Jones et al., 2013).

A positive test for blood indicates the presence of hemoglobin, which confirms that blood is present at that location or on that item. This supports the possibility of injury, violence, or contact with blood. A positive semen test indicates the presence of seminal fluid, which can link a suspect or victim to the scene or activity. Saliva testing confirms contact with saliva, which can be relevant in cases of biting, kissing, or oral contact. Each positive test provides corroborative evidence that can connect a person to a specific location or event, strengthening the forensic case (Hanson & Hamel, 2010).

The tests for blood, semen, and saliva share similarities because they are based on biochemical reactions that detect specific enzymes or proteins unique to each fluid. Most presumptive tests are colorimetric and rapid, allowing forensic scientists to screen evidence efficiently. They often employ reagents that react with hemoglobin, acid phosphatase, or amylase. Despite their similarities, the tests differ significantly in their specific targets and reactions: hemoglobin detection relies on peroxidase activity of hemoglobin leading to a color change; semen detection targets acid phosphatase enzyme activity; saliva detection depends on amylase enzyme activity. Confirmatory testing, such as enzyme-linked immunosorbent assays (ELISA) and DNA analysis, is used to validate presumptive results and establish individual identities (Cowley & Evans, 2011; Hanson & Hamel, 2010).

In conclusion, the integrity of evidence collection, careful transport, and accurate testing for body fluids are crucial in forensic investigations. Recognizing the similarities and differences among tests for blood, semen, and saliva enhances the forensic scientist's ability to interpret results effectively. Proper application of presumptive and confirmatory tests provides reliable evidence that can link individuals to a crime scene, contributing to the administration of justice.

References

• Cowley, J., & Evans, J. (2011). Forensic Science: An Introduction to Scientific and Investigative Techniques. Elsevier.
• Hanson, G. P., & Hamel, J. (2010). Forensic Science: Evidence Collection and Analysis. CRC Press.
• Jones, A., Smith, R., & Taylor, L. (2013). Forensic Serology and DNA Fundamentals. Wiley.
• Saferstein, R. (2015). Criminalistics: An Introduction to Forensic Science (11th ed.). Pearson.
• Lynch, M., & Wang, J. (2014). Principles of Forensic Investigation. Academic Press.
• De Forest, P. R., & Rogers, C. (2012). Evidence Collection and Preservation in Crime Scenes. Forensic Essentials.
• Steele, H. (2016). Forensic Biology. Prentice Hall.
• Curran, J. (2017). Forensic DNA Analysis. CRC Press.
• Schmalleger, F. (2019). Criminology. Pearson.
• Buckle, P., & Sollund, R. (2018). Forensic Evidence and the Law. Routledge.