8 Finding and identifying criminals: forensic science after 1945
By the end of the Second World War, policing seemed increasingly comfortable with the adoption of ‘scientific’ techniques. Crime scene investigation (CSI) was being standardised with ‘innovative processes, procedures, and protocols of evidence collection’ (Burney and Pemberton, 2016, p. 5). Evidence was increasingly being analysed in police laboratories and presented as ‘conclusive’ in court.
Figure 12: Volunteers preparing for blood and saliva tests to help police find the murderer of two young girls (1987) [Description: A black and white photograph showing a room with a row of tables. Along one side of the tables sit plain-clothed police officers and on the other side men. Other men wait in chairs at the back of the room. The police officers are asking questions and filling in forms.] Source: https://www.gettyimages.co.uk/detail/news-photo/volunteers-taking-tests-to-help-police-find-the-murderer-of-news-photo/638907472?adppopup=true
In the second half of the twentieth century, while policing continued to develop and incorporate a broad range of scientific techniques, the promised ‘certainty’ which such methods were once thought to provide has been called into question.
Fingerprint evidence, for example, was for many decades presented in court by police experts as conclusive proof. A 16-point matching system was used by UK forces from 1953 but guidelines for the effective use of the system were not always followed (Leadbetter, 2005). By the 1970s, questions were being raised about the points-based matching protocols used in many countries. While still used extensively, it is now recognised that fingerprint evidence ‘should be recognised as opinion evidence, not fact’ (FIS Report, 2011, Chapter 42).
Similar issues have beset one of the most significant changes to police practices – the advent of DNA ‘fingerprinting’. Following technical advances by an English biochemist - Alec Jeffreys – in the early 1980s, it became possible to determine whether considerable accuracy whether DNA evidence left at a crime scene (in the form of bodily fluids or DNA material transferred to objects at the scene) matched the DNA profile of a subject.
Police in the UK were lauded as world leaders when, in 1986, Leicestershire Constabulary turned to DNA analysis during an investigation into the rape and murder of two teenage girls. Blood and saliva samples were voluntarily extracted from 5,000 local men and matched to DNA found at the scene. This resulted in the exoneration of an initial suspect who had confessed to one of the crimes. Police subsequently arrested and convicted Colin Pitchfork for the murders.
Activity 4 Early use of DNA fingerprinting
Click below to enlarge a newspaper report pertaining to the arrest and conviction of Colin Pitchfork in 1988. Consider the following question:
What led to Pitchfork’s arrest – was it the mass sampling of DNA from local men, or another factor entirely?
The Times, January 23 1988, p.3
Will need rekeying
Comment
This case was represented in the press as the first successful deployment of DNA evidence. In a sense this is true but, as you may have noticed, the culprit did not take the DNA tests initially but paid a work colleague to supply samples for him. It was only a tip-off given to police which led them to the suspect, who was then matched to the scene by DNA. Thus, in this case, it was arguably intelligence-led policing as much as the innovative use of DNA techniques which led to the conviction. This shows that even the most sophisticated technologies are only useful if they have the right samples and evidence to work with.
As with fingerprint matching, however, what was initially hailed as a trustworthy and certain means of ‘scientifically’ identifying and convicting criminals – a ‘forensic silver bullet’ – has recently been shown eventually to have technical and practical restrictions (Aronson, 2007, p. 1). Some of the challenges to convictions on DNA evidence have been due to poor sampling and analysis techniques, particular in private-sector partner organisations. Such problems are not unique to DNA technologies, as you will discover in the following section.