| Summary: | In recent years, the need for enhanced methods of
credibility assessment in criminal cases has become
illuminated. Especially in cases of sexual assault, the
words of the accused and complainant are often the sole
evidence available to police. Consequently, researchers and
practitioners have been searching for ways of
differentiating truthful and deceptive accounts, focussing
mainly on witnesses and victims. With its recent history,
however, assessment based on verbal clues has been somewhat
myopic and not well grounded in theory or integration. This
thesis examined a general hypothesis, based upon conceptual
information from a variety of perspectives, that reliable
verbal indicators of deception exist in the interrogation
situation. Sixty undergraduates were recruited for
participation in research addressing “security
effectiveness.” Participants either committed a theft “to
test the effectiveness of a new security guard” or carried
out a similar but innocuous task. They were then asked to
provide either: (1)a truthful alibi (2)a partially
deceptive account (3)a completely false alibi or (4)a
truthful confession regarding the theft to “an interviewer
also hired for the purpose of investigating thefts.” To
increase motivation in the interview, honest and dishonest
participants were offered a monetary incentive for
convincing the interrogator of their veracity. The accounts were then transcribed and examined for the presence of
eighteen language variables. A multivariate analysis of
variance (MANOVA) revealed a profile of three variables
which significantly differentiated the truthful and
deceptive accounts (amount of detail reported, coherence of
the account, and admissions of lack of memory). For
example, dishonest participants provided much less detail
(although not fewer words) in relating an event than
truthful participants describing a similar event.
Implications for credibility assessment in forensic
interrogations are discussed, emphasizing the need for
establishing external validity with eclectic research
strategies.
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