Polygraph relations to the crime but not the

tests were invented by William M. Marston in 1971. They
have been conducted for many years and widely used by enforcement agencies when
interrogating an offender. The lie detector machine measures their blood
pressure, heart rate and respiration while the law asks questions related to
their offence. One method of polygraph is Comparison Question Technique, or CQT,
which compares responses to relevant questions with responses to control
questions (Elaad, 2003). Control questions are used to deal with relations to
the crime but not the crime itself. This is to test the criminal, evoking them
to lie. Relevant questions address the crime and can be very specific. It’s
been said that guilty people should show more psychological responses to
relevant questions rather than control questions. The Comparison Question
Technique is very popular amongst law enforcement, forensics and national
security screening due to its accuracy, although its caused controversy. These
underlying problems are mainly theoretical. There’s no evidence that certain
psychological responses are related to deception; innocent people could just be
naturally nervous when asked questions. This can show that polygraph tests are
not always accurate or reliable. The lack of standardisation means that much
depends on the skills of the individual polygraph examiner who formulates the
questions. This essay will look at the advantages and disadvantages of polygraph
testing and the CQT when catching criminals who have committed sexual offences.

                  Gannon, Wood, Pina, Vasquez and Fraser (2012)
carried out a pilot study to see whether mandatory polygraph testing should be
rolled out across England and Wales. They wanted to find out if testing would
make offenders more honest when asked certain questions, while supervised by
their managers. They found there was increase in clinically significant
disclosures which can change how they’re treated in prison. This study has been
criticised as the results were based more on the belief that the test would
show that the offender was lying rather than when. This throws doubt on the
reliability of polygraph testing.

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critical review by Meijer, Verschuere, Merckelbach, & Crombez (2008) shows that recidivism is a serious problem
among sex offenders and must be reduced. This has shown a major increase in
using polygraph tests to assess convicted sex offenders. This is due to it
being compared to the urine test analysis that is used on drug addicts (English, Jones, Patrick, & Pasini-Hill, 2003). Both of these methods have shown to be accurate
when validating an offender’s truthfulness.



                  Over the years, probation officers have been
trained to carry out polygraph testing on sex offenders. This is to make sure
that sex offenders are caught in time before more serious offences are caused,
such as rape. Sex offenders are less likely to confess their crime compared to
paedophiles and they may even argue their case in court to try and get a
lenient sentence. Unfortunately, this can lead them to re-offend. Polygraph
testing can be known to produce prediction errors, such as false positives and
false negatives. False positives are when innocent people are deemed guilty and
they have a higher rate of community supervision. False negatives are the
opposite with guilty people regarded as innocent and getting lower supervision,
making it easier for them to re-offend.

understand a sex offender’s behaviour, past or current, they are asked to complete
a sexual history disclosure test. This requires offenders to complete a form listing
their offences and victims. This list is then discussed by their supervisors
and therapists. Levenson (2009) argued that social workers are unable to assess
risk without essential past history. Without this information, it is not known
whether the offenders are just a risk to adults, or children as well. Cook
(2011) carried out a between-subjects test by taking a sample of 166 sexual
offenders, who were convicted between January 1999 and August 2005. These
participants were male and had been convicted and supervised locally. They were
split into two groups: 93 received the sexual history test and 73 did not. Findings
showed that those who had undergone the sexual
history polygraph examination were less likely to re-offend.

                  Children are known to be victims of sexual abuse. This
is said to be linked to offenders’ cognitive distortions. They may minimize
harm caused by the abuse, perceive children as desiring sexual contact with
adults, or perceive their sexual contact as socially acceptable (Gannon & Polaschek, 2006; Ward, Hudson,
Johnston, & Marshall, 1997). A way to reduce cognitive distortions is
to ask straightforward questions. Examiners are unable to determine whether the
offence took place, so they have to formulate their questions more vaguely.
Offenders may be questioned about sexual contact but it could be normal
interaction; the examiner doesn’t know. Due to cognitive distortions, the
offender may not respond, leading to a false negative outcome.


are many factors that can affect the accuracy of CQT. One is repeated testing
of the same offender. Andreassi (2000) states that physiological
responses decrease when constantly triggered and can cause an incentive in the
offender. Repeated testing may force offenders to start using countermeasures
to alter test outcomes. This can be both physical or psychological techniques,
such as “fooling” the machine or unable to use the results in court. Unfortunately
for examiners this is easily undetectable and can be troublesome. Re-testing
the same offender multiple times can not only


post-conviction sex offender polygraph test has been said to have an effect on
reducing recidivism. However, there is no proof that this is true. Grubin,
Madsen, Parsons, Sosnowski, & Warberg (2004) thought that the polygraph
test would influence offenders’ behaviour therefore expecting to see a
reduction in high risk behaviour. Their study showed that using PCSOT can
reveal new information this doesn’t stop offenders from participating in high
risk behaviour.

                  There has
been some debate among critics about how ecologically valid CQT is.  It’s been argued that there’s no way to know
how strong responses may show signs of a criminal’s guilt and it could be that
the suspect is innocent. This is due to fear of being detected. Laboratory
studies have been known to lack ecological validity due to a non-real-life
setting. Participant’s wellbeing is not affected by failing the Comparison
Question Technique. 



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