Sharing Spit Forces Changes In DNA Testing
In a recent paternity test, a DNA sample was taken from a suspected father in the case. For quite a few years now, samples are usually taken from mouth to collect saliva cells to conduct the DNA analysis.
In the Journal of Forensic Sciences, Dr José Antonio Lorente Acosta (director of the Laboratory of Genetic Identification of the University of Granada) explains how saliva samples were collected from the subject’s mouth using the standard swabbing method you’ve probably seen on CSI dozens of times.
However, the saliva analysis (epithelial cells from the interior of mouth) taken from the person gave an incongruous result, a DNA which could not come from the man who had carried out the test.
After repeating the analysis, there was an only one possible conclusion: In the mouth of that man there was DNA from two different persons.
After dismissing other possibilities, the question was: how was it possible? The analysts met with the person in question and showed him the results and explained that they thought he was purposely trying to manipulate the samples which could get him in serious trouble with the judge in the case.
Faced with the evidence, he admitted that shortly before the mouth swab he put someone else’s saliva in his mouth, saliva that he had kept in a little container for the moment. This will cause a change in the protocol for the process moving forward; it will be compulsory for the donor to wash his mouth out before a witness.