Interrogations-and-Confessions-Handbook

The Effects of Drugs and Alcohol upon the Reliability of Testimony 419
the management of opiate addicts in police custody. These articles provide a
useful conceptual framework for assessing the difficulties that can arise when
opiate addicts are interviewed in custody.
Lader (1999) also provides a useful review article on the varied effects of
drugs on the behaviour of potential witnesses. The focus in his article is on
prescribed drugs, although the effects of illicit drugs and alcohol are also discussed.
The limitations of this article are that it does not provide a good review
of studies directly relevant to the management of drug addicts in police custody,
and there is no discussion on the effects of withdrawal symptoms on the validity
of witnesses’ accounts.
According to Lader (1999), generally speaking, drugs will either increase
nervous activity in the brain or decrease it. However, drugs, including alcohol
and other sedatives, may produce a ‘biphasic’ response depending upon the
dose consumed. For example, at low doses alcohol and tranquillizers will decrease
inhibitory activity of the highest functions of the brain, which has the
effect of increasing general brain activity, whereas at higher doses, the excitation
of the brain is directly reduced and the person may become withdrawn
and less active (e.g. alcohol consumption may initially make the person more
open and talkative, but with increased intake of alcohol he or she may become
withdrawn).
Lader (1999) lists the types of drug that he considers are relevant to the
validity of testimony as follows.
� Drugs prescribed to treat psychiatric disorders. These include tranquillizers,
sleeping tablets, antidepressants and antipsychotics.
� Drugs used to treat neurological disorders that have psychological sideeffects
(e.g. anticonvulsants and antiparkinsonian drugs).
� Drugs used to treat non-nervous disorders that in some cases may have
psychological side-effects.
� Illicit drugs, which are used by drug addicts in non-medical contexts.
� Alcohol, which has sedative effects similar to that of tranquillizers.
According to Lader, the main drug-induced states that are relevant to testimony
are sedation, disinhibition, paradoxical reactions and alterations in concentration,
memory and learning. Paradoxical reactions do sometimes occur with
drugs (i.e. these are reactions that are opposite to those normally expected). This
includes, for example, increased anxiety, anger and violent outbursts, which
is sometimes seen during alcohol intoxication. There is no mention by Lader
of how alcohol and/or drugs may influence the person’s suggestibility during
interviewing.
Tranquillizers and other sedatives, except at the lowest doses, will impair
cognitive functions, such as concentration, memory and learning, in normal
individuals. Among highly anxious persons these cognitive functions are often
already impaired due to the high level of anxiety, and a low to moderate dose of
a sedative may reduce the level of anxiety to the extent that cognitive functions
are improved. However, at high doses it is likely that the anxiety-relieving properties
of the drug will not outweigh its direct depressant effects, thus leaving
the person’s cognitive impairment no better than it was, or even exacerbating it.