He joined the Metropolitan Police Forensic Science Laboratory (MPFSL, later the London laboratory of the Forensic Science Service) in 1974 as a biologist, examining body fluids and undertaking blood grouping.
In 1986 he transferred internally to the Fire Investigation Unit, the first biologist to do so, where he investigated many suspicious fires and gas/vapour explosions. He later became a Specialist Adviser (serious crime) then moved back into biology work, retraining in DNA profiling techniques. After a period as a team leader he transferred to the FSS Chepstow Laboratory and continued his work in management, body fluids, blood pattern analysis, DNA and fibres and became the laboratory’s lead scientist for fire investigation. In 2010 he became an independent consultant.
David has also undertaken critical laboratory reviews in Canada and the USA, and has trained police officers, scenes of crime officers, fire service personnel and others in various aspects of forensic science. David has been involved in mentoring and coaching other scientists including new recruits in reporting and court presentation skills.