DNA sampling. Policeman taking a DNA (deoxyribonucleic acid) sample from a woman who had been arrested. He is holding a swab, which is used to sample cells from the inside of the cheek. The sample is sent to a forensics laboratory where the DNA is sequenced and added to the National DNA Database (NDNAD). With the exception of identical twins, every individual's DNA is unique. Every person that is arrested must supply a DNA sample that can be compared to samples already held on the NDNAD. The NDNAD was set up by the Forensic Science Service in 1995.