Using Forensic DNA/ Forensic Samples with a Low Success Rate

14 Aug 2017

DNA testing allows the use of many DNA samples. A paternity test and all tests the company offers can usually be done with many potential sources of DNA. For each DNA source, the company you choose will advise you accordingly regarding the rate of success and how likely it is that the DNA sample provided will give conclusive results.

Why do Companies Encourage the Use of a DNA Saliva Sample?

Saliva is typically sampled (samples meaning ‘collected’) using a sterile mouth swab which you can purchase from any pharmacy. You can take you own DNA saliva samples by rubbing the swabs in your mouth to collect cheek cells (or what would be referred to as exfoliated buccal epithelial cells). The procedure is non-invasive and painless and has an excellent success rate; in other words with a saliva sample you DNA test is extremely likely to be concluded.

Can I use a blood DNA Sample for my Paternity DNA Test?

Using blood when one has the option to use saliva does not make sense. Blood DNA samples are now obsolete in DNA testing (though blood samples are still used for other medical tests). Blood draws, which are inevitably needed to collect a blood DNA sample, are invasive as a needle is required to puncture the skin (venepuncture) and extract the blood. Such a process can be quite frightening for children and adults too may find it distressing. However, if blood is taken using medical blood draws the success rate is extremely high, around 99%; keep in mind the postage of such sample can be problematic especially if it is going to cross national borders. Also consider the added costs involved in having a medical doctor take the blood; such costs are not covered by the company offering your paternity DNA test. Blood samples using tampons or a blood stained tissues offer a lower success rate of around 75%, depending on how old the sample is and were the tissue has been stored.

What are Low Success Rate Samples in DNA Testing?

There are too many possible DNA samples available to be discussed in an article. The following are low success rate samples.

DNA testing with Envelopes: with a success rate of just 25% envelopes are not exactly the ideal samples. Can you be sure the person even licked the envelope? If the envelope remained in damp conditions for a length of time, this may affect the success rate.

Cigarette Butts: cigarette butts would require a number of butts to being with. Moreover, some people are what are called ‘dry smokers’ and do not actually wet the end of cigarette with their saliva or just touch it to their lips rather than place it between their lip and in their mouth. If cigarettes have been wet with saliva and between 3 and 6 are provided, then the success rate is around 65%.

Hair DNA sample: Hair DNA testing has a good success rate for a paternity DNA test only if it has the root attached. This means that hair that has been cut will likely not be useful to extract DNA. Waxed hairs may also not be ideal even though they do normally have the root. This is because waxing may use certain chemicals to pluck the hairs that may degrade the DNA sample.

Pacifier: many times pacifiers are not good as parents and others may handle the pacifier over and over thus contaminating the sample with multiple DNAs.

Advanced DNA Testing for Low Success Rate Samples

Some DNA testing companies may be able to carry out a paternity DNA test using samples that they do not ordinarily test or advertise. You may for example have a single cigarette butt, a single hair sample or a sample that may have been exposed to, for example, boiling or chemicals. Testing DNA samples under advanced laboratory testing conditions means analyzing samples in much more detail, with less DNA available and with samples that may have been degraded (such as the ones here mentioned). Such advanced testing may be challenging for laboratory analysts. Advanced DNA testing can be done; however, always seek the advice of the paternity testing company who can offer the best possible advice on DNA samples and alternatives you may not have thought of or know about.