Collecting trace DNA and touch samples from crime scenes has long been a significant tool in forensic investigations. The ability to generate DNA profiles from these traces is a critical element of forensic evidence that aids in inculpation or exoneration of criminal activity. However, there are circumstances where these traditional collection methods may not be sufficient to assist in a case. Fortunately, the emerging field of environmental DNA (eDNA) and its applications are opening up new and exciting avenues for forensic evidence, particularly in the potential of airborne DNA.
For instance, a study conducted by researchers at Flinders University revealed that even the circulating air can contain trace DNA from people, which can be collected using simple methods such as dry swabs. The eDNA can then be analyzed to identify the person responsible for leaving it behind. This versatile technique holds promise in forensic investigations of crime sites that have been wiped clean of fingerprints and trace evidence, offering a new ray of hope in such cases.
It’s not just human traces that can be collected from the air; the same method can also be used to gather DNA from animal species. Researchers have tested a series of rivers in the US and Ireland, gathering swab samples from various locations and matching them to a range of known animals such as fish, birds, and mammals.
Another new technique that is gaining ground in the scientific community is air and dust sampling. While the forensic potential of this is yet to be fully explored, it is likely to prove an important new tool in the fight against a number of environmental and human health threats. This wide range of applications underscores the potential of these techniques, inspiring further exploration and innovation in the field.
It has been shown that a wide variety of human DNA can be released into the environment due to certain activities such as talking, coughing, or shaking. This DNA can then be dispersed into the atmosphere, where it can be ingested and carried on wind currents to various surfaces. In addition, shedding skin cells and other biological material can release DNA into the environment after some time. This DNA can be deposited on various surfaces, such as clothing and bedding.
Moreover, it has also been shown that DNA can be released from surfaces following gentle agitation and transferred to other items such as clothing, pillowcases, and towels. In one study, Thornbury et al. [109] examined this phenomenon by gently shaking items such as clothing, pillowcases, and a towel and then collecting and analyzing the secondary surfaces. In 87% of the cases, a complete profile of the item owner was detected.
Furthermore, in a study by Fantinato et al. [90], air and dust samples were collected from different locations within an institute. When these were compared to DNA profiles of individuals occupying the rooms, it was possible to identify them. The authors note that further studies are required to evaluate the relative DNA contribution from air and dust for occupants in spaces of varying sizes, configurations, levels of occupancy, duration of occupancy, activity during occupation, positioning of occupants within the space, and other factors.