Plucking key evidence from air

PhD candidate Emily Bibbo and Dr Mariya Goray at the DNA forensics research room at Flinders University.
Photo Credit: Courtesy of Flinders University

Culprits may one day be found using a new technique to potentially pick up and record key airborne forensic DNA evidence from crime scenes wiped clean of fingerprints and other trace evidence.

A new study led by Flinders University forensic science researchers puts the new method to the test with conventional air-conditioning units as well as a portable, commercially available air collection device regularly used to test for COVID19 and other airborne viruses in hospitals, schools and nursing homes.

“Human DNA can be found in the air after people have spoken or breathed (via saliva droplets), shed skin cells or dislodged and aerosolized from surfaces and collected for DNA analysis,” says Emily Bibbo, a PhD candidate at Flinders University’s College of Science and Engineering.

“We may be able to use this as evidence to prove if someone has been in the room, even if they wore gloves or wiped surfaces clean to remove the evidence.”

Collection of trace DNA, comprising just a few human cells, is commonly used in criminal investigations. For example, 62% of all samples processed by Forensic Science SA in 2020 were trace or touch evidence, yet success rates with this type of evidence remain poor.

Decomposition under the microscope

Lara Indra photographically documenting an animal cadaver. Attached to the tree trunk and behind the researcher are camera traps; an insect trap is positioned to the left.
Photo Credit: Sandra Lösch / Dept. of Anthropology, IRM, University of Bern

Researchers at the University of Bern have investigated the process of decomposition on pig carcasses left in nature. The researchers discovered that the previous standard method for assessing decomposition in Switzerland needs to be adapted – with an impact on forensic analysis. The method presented by the researchers aims to better determine the post-mortem interval.

A dead body decomposes with the help of various organisms – such as intestinal bacteria, flies, maggots and beetles. This makes it difficult to establish the post-mortem interval of cadavers in forensics: the more advanced the decomposition, the harder it is to determine the time of death. Therefore, various methods have the goal of correlating the degree of decomposition with the postmortem interval. With respect to this, the body is divided into three areas – the head and neck, the trunk and the extremities – and its condition is assessed using a point value system. The findings from the three areas are then added together, resulting in the total body score (TBS).