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Hair in Forensic Analysis

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Anna Schmitz

on 1 May 2016

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Transcript of Hair in Forensic Analysis

Hair in Forensic Analysis
Hair can be a helpful source of information in crime scene investigation because of its ability to stay intact for long periods of time, unless it is burned.
Results of Analysis
Drugs, chemicals, and biological substances accumulate and are stored in hair and nails where they can be detected and measured.
Age recognition can be approximated into age groups i.e. infants hair appears finer and less distinct under a microscope. The loss of pigmentation is an indicator of an older age.
Advantages vs. Disadvantages
The Science
Only one tenth of a single percent of DNA differs from one person to the next.
Scientists can extract DNA from sample of blood, bone, hair, and other body tissues.
Samples are compared to each other to check DNA resemblance.
Expanded rapidly after microscopic hair examination became known in the early 20th century.
Forensic hair analysis has played a major role in court cases since the beginning of the 1900's.
France 1857 introduced the first forensic science reports involved scientific study of hair.
In 1977 John Hicks "Microscopy of Hairs: A Practical Guide and Manual" laid out groundwork for the use of hair evidence
Follicle must be intact for DNA analysis.
High contamination rate because of humans constant shedding of hair
Easy non-invasive collection
Small sample size
Easy room temperature storage
What is a hair analysis test?

Hair analysis is a test in which a sample of a person's hair, generally from the back of the neck, is sent to a laboratory for measurement of its mineral content. Hair analysis is used to determine values for many minerals simultaneously.

Can the racial origin of hair be determined?

It can help rule out suspects. African American hairs, for example, are normally kinky, containing dense, unevenly distributed pigments. Caucasian hairs are straight or wavy, with very fine to coarse pigments that are more evenly distributed when compared to African American hair. Sometimes a cross-sectional examination of hair may also aid in the identification of race.

Can you get DNA from hair?

And a hair shaft simply doesn't contain nuclear DNA. In other words, you can only do one of the three types of DNA testing on a lock of hair that doesn't have a root or follicle attached, and that's the mtDNA testing.

What can be detected in a hair sample?

Hair analysis may refer to the chemical analysis of a hair sample, but can also refer to microscopic analysis or comparison. Chemical hair analysis may be considered for retrospective purposes when blood and urine are no longer expected to contain a particular contaminant, typically a year or less. Hair analysis are typically used for distinguishing between species and suspects, DNA analysis at the follicle, and drug testing.

What is a strand of hair composed of?

Hair is composed of the keratin, the protein also found in your nails. Hair is produced at the follicle. Hair color results from chemical compounds call pigments that reflect certain wavelengths of light. Hair structure has three main parts; the cuticle, the outing coating of overlapping scales, the medulla, the central core that may not be present, and the cortex, the protein rich structure surrounding the medulla that contains the pigment.

What is the medullary index and why is it important?

The medullary index is the fraction of the hair shaft's diameter that the medulla occupies and tends to ne generally less than 1/3. Other species will have ratios much larger, usually at least 1/2. The medulla's presence in human hair and the patterns of which differ both from person to person and from strand to strand on a single person's head, some may have complete or fragmented medulla. For this reason, medulla patterns are not very useful as forensic evidence and are typically only used for determining the species of the subject.

Unfortunatly for Santae Tribble, who was convicted of murder at age 17 in 1978, the scientific deniability of forensic hair evidence was not as advanced as it is now. FBI investigators “proved” Tribble’s hair was found at the scene. Tribble continually denied the charges and after 28 years in prison, the evidence was reexamined and not only found that the hair was not Tribble’s but that the evidence collected from the scene belonged to a dog. Tribble was released with certificate of innocence in 2012. This launched investigation into more FBI cases predating 2000, where many more flaws were found.
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