When a police officer 1 obtains a DNA sample from someone in a criminal investigation, then the sample is either a blood sample (usually taken as a fingerprick) or a mouth swab (called a buccal sample). People always take the mouth swabs themselves. Blood samples are taken by qualified people.
Once obtained, the DNA sample is carefully labelled and packaged up so it does not get contaminated. It then goes to the Institute of Environmental Science and Research (ESR) for forensic scientists to process. From the results, the scientists produce a DNA profile, which is a series of numbers. (See more information on the difference between DNA Samples and DNA profiles)