Forensic Hair Examination Notes

Forensic Hair Examination Overview

  • Introduction to Forensic Hair Examination - Hairs are frequently recovered at crime scenes since individuals shed between 50 and 100 hairs daily, presenting a source of evidence that can link suspects to victims or crime scenes.

    • The sturdy nature of hair makes it good forensic evidence, as it can survive for many years under various environmental conditions, which enhances its relevancy in long-term investigations.

    • Hair allows for rapid and cost-effective microscopic examination due to its abundance and the relative ease of retrieval.

    • Hair contains valuable biological information, including extractable nuclear DNA and mitochondrial DNA (mtDNA), which enhances its usefulness in forensic investigations and can assist in establishing identity or familial relationships.

Hair Growth and Structure

  • Durability and Preservation - Hair is among the most durable natural materials found at crime scenes, often preserved intact even after many years, making it a reliable source of evidence.

    • Only mammals possess hair, which grows from the epidermis in follicles that contain blood vessels, nerves, and sebaceous glands, providing nourishment and support for healthy hair growth.

  • Keratinisation - Hair is made of keratin, a fibrous protein that hardens as it emerges from the follicle, providing strength and resilience.

    • Key growth phases include:

      • Anagen (2-7 years) - This is the active growth phase where new cells are generated rapidly at the root. Hairs can be long and well-nourished during this phase.

      • Catagen (2-3 weeks) - The transitional phase where cell production slows, and the follicle begins to shrink; hair growth ceases.

      • Telogen (about 100 days) - This is the resting phase where hair is shed mechanically, signaling the end of the hair's life cycle once dried and detached from the follicle.

  • Hair Structure - Hair consists of three main parts:

    • Root - The attached end of the hair, embedded within the follicle, playing a critical role in hair growth.

    • Shaft - The visible part of the hair, which can vary in shape, color, and texture.

    • Tip - The opposite end from the scalp, which is often used in forensic analysis to evaluate the age and condition of the hair.

    • Microscopic Composition:

      • Cuticle - The outer layer featuring overlapping scales that help distinguish between human and non-human hairs, as well as identifying potential alterations from various treatments.

      • Cortex - Contains pigment granules and cortical fusi, which are crucial for individualization of hair samples, aiding in matching hairs to specific individuals.

      • Medulla - The inner core, which varies in structure and can serve as another key identifier, providing additional characteristics for comparison.

Comparison of Human Hair

  • Types of Human Hair - Human hair exhibits diversity, including different types such as head, pubic, facial, chest, armpit, eyelash, and limb hair.

    • Typically, only head and pubic hairs are considered suitable for microscopic forensic analysis due to their distinctive characteristics.

    • Pubic hair is usually shorter, has a wavy or curly shaft, and features pointed tips that can provide clues about the body's condition at the time of shedding.

    • Various hair treatments (such as dyes and perms) can also serve to differentiate samples based on age, treatment type, and the specific characteristics introduced by such procedures.

  • Forensic Application - Known samples from suspects are commonly collected by law enforcement and subjected to comparison with questioned samples found at crime scenes.

    • A comparison microscope allows for detailed side-by-side examination of samples, enhancing the opportunity for accurate assessments.

Forensic Hair Comparison Methodology

  • Microscopic Examination - The microscopic examination process is critical; conclusions are drawn based on differentiating characteristics, such as color, shape, and texture.

    • Possible outcomes from comparisons can include:

      • Hair matches a known sample (though this is not a definitive identification).

      • Hair has similarities but also differences; deemed inconclusive for forensic specifics.

      • Hair does not match at all, indicating a lack of connection between the samples under scrutiny.

  • Expert Commentary - Dick Bisbing (2001) emphasizes the necessity for agreement on multiple traits without fundamental dissimilarities to reach a credible identification conclusion, reinforcing the importance of thorough analysis.

DNA Analysis of Hair Samples

  • Advancements in DNA Analysis - Mitochondrial DNA (mtDNA) analysis represents a significant advancement, allowing for DNA identification even from shed hair at the telogen phase, which traditionally posed challenges for individualization.

    • Mitochondrial DNA analysis can differentiate similar-looking hairs that cannot be effectively matched through microscopic examination alone, thus enhancing the evidentiary power of hair samples.

  • Complementary Methods - The integration of microscopic analysis with mtDNA testing can complement forensic examinations, providing a higher level of reliability and detail, thus improving the assessment of hair evidence in investigations.

Case Study: THE QUEEN v STEVEN SHEPHERD (2005)

  • Background of the Case - Steven Shepherd was convicted of the murder of Vera Waring, identified posthumously through forensic evidence.

    • Critical evidence included several hairs found on the victim, with a matched DNA profile from a pubic hair link directly to Shepherd, demonstrating the potential of hair analysis in criminal investigations.

  • Forensic Evidence - Two hairs were thoroughly analyzed after a significant delay in testing; however, a strong mtDNA linkage was established from hairs discovered on the victim's clothing, further implicating Shepherd in the crime.

  • Ruling - The court upheld Shepherd's conviction primarily based on the strength and reliability of forensic evidence, clearly demonstrating the effectiveness of hair analysis as a vital element in the pursuit of justice in criminal cases.