12. Forensic science laboratory

In 1929, Sir Arthur Dixon, Assistant Secretary of State at the Home Office, wrote a memorandum on the need to make use of science in police investigations.

Lord Trenchard, the Metropolitan Police Commissioner, decided that although the Force, as it was then called, could call on various eminent scientists, it was time to establish science within the Force itself. The Home Secretary, Sir John Gilmour, agreed and on April 10 1935 he officially opened a Metropolitan Police laboratory at the Police College at Hendon.

During the 1930s, a number of provincial police forces started their own laboratories. One by one these came under Home Office control to form the basis of what was to become the Home Office Forensic Science Service. With a staff of about 340, including over 200 graduate scientists (many with PhD⁶ degrees) the Metropolitan Police Laboratory has become one of the world’s laigest forensic sci­ence laboratories and it is widely acknowledged as a leader in its field.

The main purposes of the Laboratory are to help London’s police to investigate crime and to provide scientific evidence and expert interpretation for the courts. Scientists examine items submitted by investigating police officers and, when necessary, they give scientific assistance and advice at scenes of crimes or other incidents.

The Laboratory uses new discoveries in science to improve the range and quality of its services. The Laboratory also trains the users of its services so that they may understand its capabilities and the significance of the results obtained. It handles more than 18,000 cases a year, ranging from theft to terrorism.

The kind of work undertaken by the Laboratory includes analysis for alcohol in blood and urine specimens in drink-driving cases; analy­sis for heroin, cocaine and other drugs; fire investigation where ar­son is a possibility, and accident investigation in particularly serious (often fatal) road accidents. It analyses natural and synthetic fibres and fibre dyes; examines guns; analyses gunshot residues; exam­ines documents in cases of suspected fraud and other serious incidents; and analyses tool and other kinds of marks. Footwear marks continue to be a valuable aid in crime investigation, especially for armed robberies.

Scientists also analyse poisons and noxious substances of vari­ous kinds, as well as traces of paint, glass and other materials. Blood grouping and DNA profiling form an increasingly important part of the work of the Laboratory.

Forensic science is a demanding profession, because scientists may have to appear in court as Expert Witnesses. Whereas most people are only allowed to give the court evidence about facts - what they personally saw or heard - an Expert Witness advises the court on what interpretations the evidence will bear and what interpreta­tions it will not bear. In these circumstances scientists can expect to be subject to searching cross-examination.