O Distinguish Between Human And Animal Hair, Forensic Scientists May Look At What Part Of The Hair?

Hair Analysis in Forensic Science

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• Pilus Evidence
• Pilus Comparison Microscopy
• Factors to Consider
• The Suitability of Pilus for Deoxyribonucleic acid Analysis

Hair samples are i of the nearly of import resources in the forensic analysis of crime scenes, oft providing valuable information that can help to lead to the identification of a suspect or victim.

Hairs are slender fibrous outgrowths projecting from the peel that possess dissimilar microscopic characteristics such as shape, color, and root appearance. Variability in such features tin can help forensic scientists to determine age, gender, and racial origin of the person that shed the hair, equally well as assuasive ane to make up one's mind which expanse of the body pilus has come from. Hair tin can also be used to extract Deoxyribonucleic acid for analyses that tin can help to narrow down who may have been involved in a law-breaking.

Man pilus under microscope illustration. Image Credit: Kateryna Kon / Shutterstock

Hair Testify

Humans shed an average of approximately 100 head hairs per day, and because hair can exist hands transferred during concrete contact it is commonly submitted as forensic testify to help establish associations between people (e.g. a victim and doubtable) and/or people and a law-breaking scene.

Such associative evidence is especially useful in trigger-happy crimes where physical contact is likely to take occurred such as sexual set on, homicide, and aggravated set on. Crimes less likely to have involved concrete contact such equally armed robbery would typically involve collecting clothing or other items that may accept picked up hair that could be used to identify suspects.

Examination of hair by microscopy can help to establish whether a hair was forcibly removed, diseased or treated with an artificial substance such every bit a hair dye. Forensic analysts use an musical instrument called a comparison microscope to view a known hair sample and an unknown sample aslope one some other to run into if they share similar characteristics and could have come from the same source.

Hair Comparing Microscopy

A comparison microscope, which is made up of two compound light microscopes connected by an optical bridge, allows the user to view a known and unknown pilus sample simultaneously. The multi-phase examination process starts with the analyst establishing whether the unknown pilus is of animal or human origin.

If it is an animal hair, the examiner tin can further identify it every bit belonging to a particular species, although it cannot be linked to a particular animal at the exclusion of other animals within the same species. Animal hairs found on items of evidence can link a suspect to a crime scene or a vehicle or location where a victim was held. Hairs from a pet the suspect owns, for example, may also be transferred to the victim when a doubtable makes physical contact.

If the hair is human being in origin, assay tin can help to distinguish betwixt individuals based on the arrangement, appearance and distribution of certain characteristics within dissimilar regions of the hair.

Factors to Consider

Many factors bear upon the robustness of pilus association analyses, including variations in the adequacy of equipment and staff experience and preparation.

Although hair microscopy is a valuable tool to use for identification purposes, accurately determining a statistical probability of a given clan is challenging, partly due to the lack of reliable quantitative cess of hair characteristics.

Even so, the analysis tin can permit one of the following conclusions to be drawn:

• Whether the unknown hair exhibits similar characteristics to the known hair and could therefore have originated from the same source as the known hair
• Whether the unknown hair is different to the known hair and could non accept originated from the same source
• Whether both similarities and dissimilarities were seen betwixt the two hairs, meaning no decision about possible source of origin can exist made

When forensic experts practice find shared characteristics between the known and unknown pilus, a statement such equally the following may be added to their written report:

"Hair comparisons are not a basis for accented personal identification. It should be noted, even so, that considering it is unusual to find hairs from two different individuals that exhibit the same microscopic characteristics, a microscopic association or match is the basis for a strong association."

In 2009, the National University of Sciences released a report called "Strengthening Forensic Science in the U.s.: A Path Forward," which stated that since the advancement of DNA analysis, microscopic hair analysis should be bars to establishing which hairs to test, and whether hairs share similar characteristics, simply should not be considered a reliable tool for the identification of individuals suspects.

The Suitability of Hair for Dna Analysis

To test the suitability of a human being hair sample for nuclear Dna analysis, hair microscopy is used to view the cease of a hair and found whether it contains a root. If and so, the sample tin be tested using a nuclear DNA testing process called Short Tandem Repeat (STR) analysis. A hair that has been shed without a root cannot be sent for this type of testing, only tin can yet be subjected to mitochondrial DNA (mtDNA) testing of the hair shaft.

A combination of microscopic hair comparisons and DNA analysis tin can provide a complementary approach that offers superior information about hair origin, compared with that obtained using microscopic hair comparisons alone.

Under The Microscope: The FBI Hair Cases | Fault Lines

Further Reading

• All Forensics Content
• Epigenetics and Forensics
• Chromatography in Forensic Science
• Overcoming Deoxyribonucleic acid Degradation in Forensic Science
• Reducing PCR Inhibition in Forensic Science

Final Updated: May 21, 2019

Written past

Sally Robertson

Sally first developed an interest in medical communications when she took on the function of Journal Development Editor for BioMed Primal (BMC), after having graduated with a degree in biomedical science from Greenwich University.

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