A human adult sheds about 1000 skin cells per cm2 per hour, causing billions of cells to be released from the body every day. This happens through epidermal desquamation, which is a continuous process that constitutes the final active step in the keratinocytes’ differentiation program. Desquamation causes a spontaneous detachment of dead skin cells known as corneocytes. The average size of these skin particles is smaller than the pores of typical clothing fabrics, allowing them to pass through and become aerosolized. Varying levels of DNA may be retained within corneocytes; enough to yield detectable profiles. DNA can be released in the air not only through skin cells but also in other forms. Dandruff constitutes part of bioaerosol material shed by humans, with a single particle containing between 0.8 and 16.6 ng of DNA. […] human DNA is present in indoor dust in sufficient quantity and quality to produce allele calls in STR analysis. […]

There are many cases in police investigations that require identification of individuals from crime scenes […] the most difficult cases involve organized crime and terrorism, where the participants may be forensically aware, hence the detection of conventional DNA and fingerprints may be difficult to achieve. […]

The high sensitivity of DNA technology makes it possible to obtain results from very low levels of biological materials (just a few cells) […]

We have used the building of our institute as the test-bed for the investigation; the experiments were conducted in 14 offices, two meeting rooms and five laboratory areas which are accessed by corridors. […]

Positive results were obtained from 93 out of 96 dust samples for one or more office occupants, resulting in a success rate of φ1 = 0.97. Only 22 of the same samples matched with a known non-occupant, giving a non-occupant success rate of φ2 = 22/96 = 0.23.

{ Nature | Continue reading }

related { DNA-based prediction of Nietzsche’s voice | PDF }

crime, genes | March 18th, 2025