Unique to each of us, our DNA nevertheless has multiple ontologies. Following dust through a crime scene, a forensic laboratory and a criminal court, we see that DNA is enacted in three different ways: as a sign, as a result and as a proof. Each of these DNAs entails its own regime of practice, codes and meaning. While forensic genetics has been associated with certainty, stability and truth, we contend that this characterisation is made possible by DNA’s multiplicities.