Hair is one of the biological materials that may be recovered from crime scenes and can provide valuable information for forensic investigations. DNA analysis of hair may help investigators associate a biological sample with a particular individual. However, the genetic value of hair depends greatly on the condition of the sample and on which part of the hair is available. Hair containing a suitable root or cellular material may provide nuclear DNA, while hair without an appropriate root may be more suitable for mitochondrial DNA analysis. The forensic examination begins with the careful collection of hair from the crime scene. Investigators document where the hair was found and preserve it in a manner designed to reduce contamination and damage. In the laboratory, the sample is examined before DNA extraction is performed. The purpose is to determine whether sufficient biological material is available for genetic analysis. Nuclear DNA is particularly valuable for individual identification because it contains genetic regions that vary considerably among individuals. Short tandem repeat, or STR, markers can be analyzed using polymerase chain reaction (PCR). The resulting genetic profile can then be compared with a reference sample from a suspect or another relevant individual. When a hair sample does not contain an appropriate root, mitochondrial DNA may provide an alternative source of genetic information. Mitochondrial DNA is present in many copies per cell, which can make it useful when nuclear DNA is limited. However, mitochondrial DNA generally provides less individual discrimination because it is inherited through the maternal line and may be shared by maternal relatives. Several challenges can affect forensic hair analysis. The amount of DNA may be very small, and genetic material can become degraded because of heat, moisture, sunlight, and other environmental factors. Contamination during collection, transportation, or laboratory processing may also affect interpretation. In conclusion, hair can be an important source of biological evidence in forensic investigations. Proper collection, preservation, extraction, and interpretation are essential for obtaining reliable results. Modern DNA techniques have increased the usefulness of hair evidence and allow forensic scientists to provide valuable information for identifying or excluding individuals. Al-Mustaqbal University – the first university in Iraq.
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