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The Invisible Witness: DNA Evidence in Air Conditioning

Written by: Alan Baker 20th March, 2024

DNA evidence is crucial in criminal investigations. Investigators routinely collect biological material such as DNA at crime scenes and from items.

They often collect touch or trace DNA samples from surfaces and objects believed to have been in contact. However, a person of interest might not leave any traces on these surfaces, for instance, if they wore gloves.

A new method of sampling human DNA from air opens up additional opportunities for DNA evidence collection.


The Study:

To determine the prevalence and origin of human DNA within eDNA on air conditioner units, researchers took samples from air conditioning units in four offices with single occupants and four households with both adults and children.

In a study, the findings of a pilot study on the prevalence and persistence of human DNA in the air are presented.

The first part of the study focuses on air conditioning units that circulate air within a room. Researchers sampled units in four offices and four houses at various times after cleaning.

The second part examines the potential of collecting human DNA from air in rooms, both occupied and unoccupied, over different durations and using various types of collection filters.

The findings from this pilot study indicate that one can collect human DNA from surfaces of air conditioning units and from the air itself. Air samples more accurately reflect recent presence in a room, while air conditioning units capture historical occupancy.