Collecting evidence. Scene of crime officer (SOCO) writing on one of two sample collection tubes. The tubes contain swabs taken at the scene of a crime. A person found guilty of an offence by the police has to supply a saliva sample. From this a DNA profile can be formed and compared to profiles already held on the National DNA Database (NDNAD). The SOCO is wearing latex gloves to prevent contamination of the crime scene and evidence. SOCOs provide scientific support to police forces. They establish what evidence is required from a crime scene and the best way to obtain it.