Forensic exhibit packaging: paper or plastic, the potential for DNA degradation

A vital part of a forensic science investigation is the recovery of DNA from a crime scene.
Body fluids such as blood or saliva are most commonly left at the scene of a crime and are
frequently found in only minute quantities. In order to protect the recovery of this critical
evidence it is required to be packaged in such a way that further degradation of the sample
is not a possibility. In the United Kingdom, DNA evidence is packaged in plastic whereas
other countries package DNA evidence in paper. This difference is due to the belief that DNA
can degrade in plastic packaging. Evidence of a documented study that proves or disproves
this theory has not been determined so therefore a study was carried out in order to
establish which packaging would provide the most suitable option for DNA evidence. This
study investigated different drying times prior to saliva samples being stored in either paper
or plastic packaging and then determining the DNA quantities present over a set period of
time using quantitative real-time PCR. The results indicated that if a wet saliva sample was
to be immediately placed in plastic packaging and analysed within one week then this would
provide the largest concentration of DNA. If this sample was to be analysed eight weeks
after collection, the sample concentration would reduce when compared with a sample
packaged immediately in paper packaging. Even with this reduction the sample immediately
packaged in plastic presented a consistently higher DNA concentration when compared with
all of the other samples. It was determined that if the wet saliva sample was allowed to dry
for six hours and then packaged in plastic packaging, this presents the lowest degree of DNA
loss.