4.4 Credibility 153
known that they had conferred, that would
actually detract from their credibility, for it
would have to be explained why they had
conferred. If they were both simply telling the
truth, there would be no need to confer.
Corroboration is at its most potent when
there is agreement between different kinds of
evidence: for example, when statistical
evidence bears out what several independent
witnesses have said, and the circumstantial
evidence all points in the same direction. By
the same token, credibility is at its lowest
when there is a lack of corroboration, or
disagreement.• In the absence of knowledge or certainty
about the truth of some portion of
evidence, we often have to rely on its
credibility.
• There are a number of criteria by which we
can judge credibility:
• the plausibility of the claim or claims
themselves
• the reputation, expertise, independence
and/or neutrality of the source
• the ability to have seen or perceived
what is being claimed
• the absence of vested interest (or motive
for saying one thing rather than another)
• corroboration by other evidence or from
other sources.Summary
Corroboration
Each of the criteria that we have discussed
affects how we judge a claim. Yet none of
them, on its own, is sufficient to put a claim
beyond reasonable doubt. A claim is, by its
nature, uncertain, whoever has made it and
however plausible it may be. Corroboration
has been discussed at various points already,
so that it doesn’t need any further
explanation. Of all the criteria for assessing
credibility, it is perhaps the most potent. This
is hardly surprising, since it is not really a
single reason to believe a claim, but a
combination of reasons supporting and
endorsing each other.
The simplest form of corroboration is
agreement – though it must be agreement
between independent sources. If two or more
people make the same claim, or express the
same opinion, there is more reason to believe
it than if one person alone has made the
claim. It is crucial to add the word
‘independent’ here, because if it is found that
one person has influenced the others, the
added credibility is cancelled, for they are
effectively making a single, repeated claim
rather than several separate claims which
genuinely corroborate each other. You may
recall that in the previous chapter, the police
interviewed Amelia Jackson’s flatmates
separately. The fact that they still gave the
same answers added to the credibility of what
they said, but there was still the possibility
that they had conferred in advance, and
anticipated the questions. Indeed, if it is
and, most importantly, why you reached those
decisions.)
Read the following passage carefully and
answer the questions that follow.This assignment can be completed
individually in writing, or as a group
discussion. (If you choose the second of
these, you should also make notes on what
you discussed, what decisions you came toEnd-of-chapter assignment