The role of the forensic scientist is to carry out appropriate scientific examinations in support of the investigation of crime. Through advances in science and technology and with less reliance being placed on other types of evidence such as admissions or witness evidence, forensic science has become one of the principal means of investigating crime.

Traditionally, forensic science has been associated with providing objective corroborative evidence that supports or refutes other forms of evidence so often seen as being more subjective. However, forensic science is being used increasingly to support the early stages of an investigation by providing forensic intelligence. It is this use of forensic science, principally through DNA analysis and the use of DNA databases, which has seen a significant increase in the use of forensic science by police forces in the UK.

While most of the work of the forensic scientist is carried out at the laboratory, the forensic scientist may also undertake examinations at the scene of crime (see previous chapter). Examinations at the scene may be vital in helping to establish exactly what went on. The interpretation of bloodstains can help to identify the location and nature of an attack. The identification of several seats of burning may establish the cause of a fire as arson. Attending the scene also allows the forensic scientist to select the most appropriate material for detailed examination at the laboratory.