How Hair is Used in Investigations

• Fluorescence Microscope: Shines colored beams of light through an object to cause certain chemicals reemit light of a different color

  • Helps indicate the presence of dye

Testing for Chemicals in Hair

• Chemicals that are absorbed in the skin can be incorporated in hair as it grows

  • Only a few millimeters are needed

• Is used to back up blood and Urine tests because the chemicals remain longer

• Can be tested for Heavy Metals

  • The hair is dissolved to release any possible chemicals for analysis by a chemist

Testing for Chemicals in Hair

• Oils in the hair can absorb chemicals from the environment

  • A person may not have ingested poison, but it may show up in their hair

• False Positive: A test result that indicates something that may not be true

Testing for Chemicals in Hair

• We can use the same conversions for hair growth and dyeing for poisoning

  • Poison does not spread in the shaft, and is only located in the areas growing when exposed

• Example: A person is brought to the hospital with symptoms resembling chronic arsenic poisoning. When studying the hair shaft, they found that the toxin first appears 1.3 cm away from the root. How many days has it been since the victim was poisoned?

  • Step 1 set up your conversion factor

Neutron Activation Analysis

• A mean of identifying an individual based on hair

• looks at the concentration of 14 different elements in a hair shaft by bombarding them with radiation

  • Each element gives a different response

• The probability of two individuals having the exact same concentration for any nine of the elements is ~ one in a million

Testing The Hair Follicle

• Follicular Tag: The presence of the entire follicle on a hair sample

  • Happens when a hair is removed by force

  • Can be used for DNA Testing

    • Generally done after microscopic analysis to save time and money