What the DNA Tests Cannot tell You

DNA testing is a secure means of establishing paternity issues and finds extensive use in relationship tests and many other tests. Given the growing use of DNA testing, it makes sense to be aware of what a DNA test can or cannot do and highlight some of the common queries people have.

DNA Testing is Reliable for Many Reasons

The discrimination between DNA samples is immense. The chances of one person randomly selected from a population having the same DNA as yours are negligible and thus, so small that they are most times not even taken into account.

DNA is found in all nucleated calls throughout the body and thus, testing can use a number of medium to extract DNA. Amongst viable samples would include semen, skin, internal body membranes, hair, teeth and mucus. Advances in the field of DNA testing, especially in the use of what is known as ‘polymerase chain reaction’ allows even the smallest DNA samples to be used as these samples can be replicated and amplified. Moreover, another advantage is that our DNA is relatively stable under normal environmental conditions and will remain unchanged for a very long time, even centuries.

The Unreliability of DNA Testing in Court Cases

Many police investigations often inevitably reveal sources of DNA which become invaluable tools to tracking down the perpetrator. In the court room, the defense often criticizes the inconsistencies or unreliability of DNA testing. They base these claims on the statistical probability that someone else in the population may have your same DNA; the probabilities are often cited, for example 1 in 50, 000,000. It is clear however, that when lawyers defend their client and dispute DNA evidence, it is because they have absolutely no better card to play.

Can I Use any Hair DNA Sample in a DNA Paternity Test?

In cases where you cannot obtain a standard saliva sample than hair could be an option. However, hair is not the most straightforward of samples. It is a sample that can easily be collected from a hair brush if for example, a test participant lives abroad. However, although the success rate with a hair sample is around 60%, this success rate is calculated under optimal circumstances. This means that hairs sent in would be at least 5 in number and more importantly, have the root or hair follicle attached. If the root is not attached it is highly unlikely that it can be used. The hair fiber does not have nucleated cells as nucleated cells are only found in the root.

However, the hair fiber contains what is known as mitochondrial DNA even if it does not have the root. Whilst Mitochondrial DNA (MtDNA) could be used for DNA testing, its use is exclusive to finding whether individuals share the same maternal lineage and thus, MtDNA samples do not find use in any other tests such as paternity DNA tests.

Non-Standard Samples for DNA Testing: Odd Questions

People wishing to use samples other than saliva DNA samples sometimes are unsure about how to send in samples. The DNA testing companies will advise you about how to collect samples properly so that they do not get contaminated and more importantly, will inform you whether the DNA sample is viable in the first place.

Fingerprints: Fingerprints are unique to the individual much like DNA.  There is such a thing as a fingerprint DNA sample. A fingerprint left on a glass may contain DNA as the contact between the glass and the finger may leave skin cells attached to the glass. The chances of being able to conclude a DNA test with such a sample is low.

DNA testing requiring alternative DNA samples to saliva DNA samples leaves many possibilities. Any surface where biological matter has been left could potentially be a source for DNA for your paternity test or a relationship test. A sweaty sock, baseball cap, deodorant stick and tooth picks; however, time, chemicals and harsh environmental conditions can all contribute to making your DNA sample useless to conclude your DNA test.