AC1.2 Assess the usefulness of investigative techniques in criminal investigations
Investigative techniques
Use of intelligence databases to investigate crime
The police use many databases to help them store and access information to assist in the
fight against crime. Examples include the UK national DNA database and Police National
Computer (PNC), which holds extensive information on people, vehicles, crimes and
property. Crimint, run by the Metropolitan Police Service of Greater London, stores
information on criminals, suspected criminals and protestors. Also, some databases contain
information from witnesses, informants and agents.
Forensics
Forensic science is very different now than it was 100 years ago. In the past, when police
had to attend a crime scene, they would be alone until a doctor arrived to confirm death
and carry out a very quick review of the body. In today’s world of forensic science:
The police are accompanied by a range of forensic experts to help in the
investigations.
The police discuss actions and usefulness of various forms of evidence with the other
experts.
There is limited access to a crime scene, and protective clothing is required to be
worn, to avoid contamination.
The police recover evidence scientifically, which is then considered by a range of
experts in many different fields.
Case study
Colin Pitchfork – One of the most useful forensic techniques is that of the use of DNA
(Deoxyribonucleic acid). This is the chemical that carries genetic information and is
contained in chromosomes found in the nucleus of most cells. Sometimes called our genetic
code as it determines all our characteristics. The first criminal conviction using DNA
evidence was that of Colin Pitchfork in 1986. Pitchfork was found guilty of the 1983 murder
of Lynda Mann and of the 1986 murder of Dawn Ashworth.
At the time of the second murder, Alec Jefferys, a British geneticist, was pioneering profiling
techniques by using DNA and was able to use his work to confirm that the two girls had
been killed by the same man. He was also able to show that Robert Buckland, who had
confessed to Dawn Ashworth’s murder, was not the Mann killer. When the police obtained
blood samples from all the men in the area, Pitchfork had persuaded a friend to
impersonate him and provide the sample. This was eventually discovered by the police who
arrested Pitchfork and were able to use Jeffrey’s DNA profiling technique to confirm him as
the double killer.
DNA can be seen as a useful investigative technique for the following reasons:
It is found in virtually every cell of the human body.
Everybody’s DNA is unique, which allows for very high reliability.
It gives the chance to solve all murders.
It can help prove innocence as well as guilt.
It can help identify victims when other methods do not work.
DNA from closely related relatives, such as siblings, have many similarities in
common.
, AC1.2 Assess the usefulness of investigative techniques in criminal investigations
However, DNA can produce limitations in an investigative technique. For example:
Cross-contamination of evidence is possible.
To secure a match with a sample from a crime scene, the perpetrator must be on the
National DNA Database.
Such a technique may infringe civil liberties, especially when DNA profiles are stored
from people who are innocent.
It is possible that trace amounts of DNA can falsely implicate a person.
The financial cost of DNA testing.
Case study
Colette Aram – Colette Aram was murdered in 1983 before DNA was established as an
investigative technique. However, as forensics developed, scientists were able to build up a
DNA sample taken from the murder scene and from the local pub the murderer had visited
after he killed Colette. Familial DNA profiling enabled the conviction of Paul Hutchinson
when a close relative had a sample taken following a driving offence. Despite Hutchinson's
sample not being on the National DNA Database, the family link was made, and a conviction
was secured 26 years ago after Colette’s murder.
Case study
David Butler – David Butler was charged with the murder of a prostitute, Anne Marie Foy, as
a result of a Partial DNA match. His DNA was found under the victim's fingernails. However,
despite being in custody was for eight months, at trial Butler's were able to show the jury
that the procedures used to obtain the DNA were unreliable, and the evidence was of poor
quality. In addition, Butler suffered from a dry skin condition which meant he shed large
flakes of skin, so his DNA was easily transferred. As he worked as a taxi driver, it is possible
that he had taken a passenger to the red-light district, where the victim worked, and DNA
was passed on in the change given to a passenger and then to the victim. This meant that
Butler was acquitted of the murder.
DNA evidence can be particularly useful in violent and sexual offences. In such cases
evidence is usually left at the scene in the form of blood, hairs or semen. This allows a DNA
profile of the potential defendant to be constructed.
Surveillance
In modern policing surveillance, CCTV is a major investigative technique that they use. It is
one of the first things an investigative officer asks for following a crime as it can provide
permanent images of the crime taking place and the pictures of the criminals.
CCTV plays a large role in everyday life and there are cameras on the streets of many towns
and cities as well as business premises and inside shops.
Case study
Colin Stagg – Following the murder of Rachel Nickell in 1992, Colin Stagg was arrested but
there was no evidence to link him to the crime. Police therefore established a ‘honey-trap’,
involving a female officer, who pretended to be interested in forming a relationship with
Stagg. Despite trying to entice him in into a murder confession, Stagg maintained his
evidence. However, information gained as a result of this covert operation was put before
the court. The trial judge described the undercover operation as ‘misconceived’ and ‘not
