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Hair DNA test Leads to Conviction After 20 Years


Unlike other criminal evidence that may be easy to remove such as personal possessions, fingerprints or footprints, hair strands are harder to detect and remove and thus very often remain at the scene of the crime. Whilst forensic testing of hair strands was first used as criminal evidence in 1861, it only gained scientific acceptance during the late 1950s.

During the 1990s, despite the initial reaction to the hair DNA test as an example of possible latter-day voodoo, Court systems generally agreed that a hair DNA test was a reliable method of providing scientific evidence to assist forensic scientists, notably from 1992 onwards when the National Research Council agreed that testing was a reliable method of identifying criminal suspects.

With the exception of identical twins, each person’s genetic identity is unique. It is this quality of uniqueness that makes DNA testing so accurate. Hair DNA is a universal, painless, confidential test result for a DNA paternity test. Performed by qualified scientists using DNA analysis techniques, it’s a quick and simple procedure only requiring a few hairs.

It is possible from sub-microscopic amounts of tissue to positively identify an assailant if it is properly collected and analysed as was proven recently in Wisconsin Rapids when a man was arrested and charged for the abduction and sexual assault of an 11-year-old girl that took place nearly 20 years ago.

Hair DNA Test – How It Works

A hair DNA test uses the DNA found in the root of a single strand of hair to create a DNA profile. A more reliable method of isolating DNA from hair shafts is alkaline extraction, where keratin from the hair strand is hydrolyzed but the DNA is kept intact.

The most recent development in forensic examination of hair is the use of mitochondrial DNA (mtDNA) testing of hairs (notably head and pubic hairs) as a safeguard for traditional microscopic examination and testing. MtDNA is found in the mitochondria, a circular structure surrounding the cellular nucleus that gives the cell energy. mtDNA is a simple testing procedure, where a microscopic examination is followed by washing the DNA to remove any contamination. It is then put into a chemical solution which causes the DNA to separate form other biological molecules such as proteins. The DNA is then spun in a centrifuge, with the DNA being soluble as a top layer of the resulting solution. This is removed, filtered and them amplified using PCR (polymerase chain reaction) and analysed for individually unique genes.

PCR involves taking a small amount of DNA and copying it using a process known as amplification, where two strands of DNA helix are separated from each other by heating the sample. Original DNA molecules separate into component strands. A new DNA strand is made which is a copy of the existing DNA molecules, with a doubling of the amount of DNA during each repetitative process.

The possibility of using DNA to provide accurate evidence invisible to the naked eye to help identify an assailant or even to prove a suspect’s innocence is still being developed, with the procedures and methods involved in DNA testing still evolving.

Further reading

DNA Hair Testing Used To Find Killer in Annie Le Case: Annie Le was a popular and friendly Yale graduate student who had the world at her feet. Nevertheless, for some hitherto unknown reason, Annie Le was killed by traumatic asphyxiation and her body was found on the 13th September 2009, having been missing for five days. Hair DNA testing was used to solve the case. Click here to read more.

Hair DNA Test Results Used As Evidence in Murder Trial: In this case, the victim’s body was found, partially clothed, wrapped tightly in bin bags and also covered in a duvet. It was located in a car park in Ireland and she was killed in September 2006. The defendent, 51, denies being guilty of the murder in 2006 between the 17th and 20th of September. Hair DNA testing was used to solve the case. Click here to read more.


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