Interrogations-and-Confessions-Handbook

The Effects of Drugs and Alcohol upon the Reliability of Testimony 425
drugs for at least two weeks. They were not currently suffering from acute withdrawal
symptoms. The two groups were referred to as the ‘detox’ and ‘rehab’
groups, respectively. They were matched for IQ and a number of drug-related
demographic variables. During the study all subjects completed the GSS 1, the
GCS, the Hudson Index of Self-Esteem (Hudson, 1982) and the Spielberger
State–Trait Anxiety Inventory (Spielberger, 1983). It was hypothesized that
‘due to increased anxiety, compliance, lower self-esteem and other physical disturbance
associated with opiate withdrawal syndrome, suggestibility would be
higher during active withdrawal than when the person is abstinent’ (p. 1367).
The data were analysed using t-tests for independent samples. The ‘detox’
group had a significantly higher total suggestibility score than the ‘rehab’ group,
the mean scores being 12.2 and 9.1, respectively. State anxiety was also higher
among the ‘detox’ group, which may explain the differences in the suggestibility
scores between the two groups. The possible interaction between suggestibility
and anxiety was not tested in the study. The immediate and delayed recall scores
on the GSS 1 were very similar for the two groups, which suggests that acute
withdrawal symptoms from opiates do not impair memory recall. A similar
finding was noted in the Davison–Gossop (1996) study.
No significant differences were found for compliance. The GCS scores for the
‘detox’ and ‘rehab’ groups were 10.2 and 9.8, respectively. Again, this is consistent
with the findings from the Davison–Gossop study and demonstrates that
the GCS, unlike the GSS 1 and GSS 2, is not a good instrument for measuring
transitory changes in behaviour.
There are important differences between the two studies discussed in this
section. Probably the most crucial difference is that in the Davison–Gossop
study testing took place at the peak of methadone withdrawal (i.e. between
10 and 14 days after the onset of withdrawal from opiates), whereas in the
Murakami–Edelman–Davis (1996) study the GSS 1 was administered prior to
the patients being stabilized on methadone. The Murakami–Edelman–Davis
study may therefore give a clearer picture of the direct effects of acute opiate
withdrawal on suggestibility than was obtained in the Davison–Gossop study
and, as the authors argue, is more akin to that found in police custody.
The main advantage with the Davison–Gossop study is that it involved a
within-group comparison in contrast to a between-group comparison. It is possible
that the ‘rehab’ group in the Murakami–Edelman–Davis study was not an
ideal control group. For example, they had a longer history of opiate abuse than
the ‘detox’ group and were more actively involved in criminal activities. We do
not know how important these factors were in influencing differences between
the two groups of subjects in terms of suggestibility. The problem with this kind
of research is the large number of patients who drop out of treatment. A good
control group is therefore probably impossible to obtain. The high drop-out rate
was also noted in the Davison–Gossop study.
The Differential Effects of Drugs on Interrogative Suggestibility
Different drugs may have differential effects on suggestibility, but empirical
research in this area is lacking. In an undergraduate project at University
College, London, Brignall (1998) compared the acute and residual effects of