It turns out that finding an uninvited guest does not necessarily require looking for fingerprints or traces on objects. Sometimes it is enough to examine the air. Scientists from Norway and Australia staged burglaries in 22 homes and detected DNA from people who did not live there in air samples from 13 of them (59%).
Volunteers spent 15 minutes opening cupboards, touching objects and talking. Half an hour after they left, the researchers collected air samples using special filters.
In one case, an air sample helped identify a participant whose genetic traces were not found on any of the objects they had touched. This is because people constantly shed microscopic particles of skin and saliva.
The method is still far from being used in real investigations: the experiments were conducted without gloves, and samples were collected just 30 minutes after the participants left. However, the results suggest that air could become an additional source of forensic evidence.
