independent of one another and thus are unlikely to have collaborated in
falsifying the evidence or to suffer from a common bias.
615
On the surface, corroboration appears to be
common sense. In truth, it is
based on probability theory pure and simple. Where the likelihood of either
collusion or common bias for two witnesses is small, there is a strong
probability that the gist of their evidence at least is true.
In summary, corroboration operates in the following way. Persons A and B
are totally independent and each observes something happening. They then
give substantially the same account of it in evidence. Then there is a strong
probability that they are telling the truth. If they are independent they have not
collaborated. Given this, the chances that both are not telling the truth but
telling the same version of the truth is slim. The overwhelming likelihood is that
what they said was substantially the truth.
This is the reasoning for that conclusion. A and B could each tell one any of
any number of false stories. From the perspective of the court, each false
story is equally liable. Let us assume for the purposes of illustration that A has
5 possible false stories and B has 4. The probability that A and B would each
tell the same false story is one in 20 (5 x 4) namely 5%. Therefore if A and B
tell much the same story, the probability that it is true is 95% (100% - 5%). In
short, it would be such a coincidence for each to tell the same untruth without
corroboration as to be highly unlikely.
In some cases corroboration is legally required by common law or statute. In
other cases corroboration is not strictly legally required but the evidence may
still be of such a kind that it needs to be taken with great care. Moreover, in
some cases a judge who does not appropriately instruct a jury to act with
caution in relation to uncorroborated evidence may be in error.
615
There is an illustration of this notion in a song, M Wilkens, D Dill Long
Black Veil, originally recorded by Johnny R Cash on 12 July 1964. Long Black Veil
opens with these words: “Ten years ago, On a cold dark night, A man was stabbed
‘neath the Town Hall light, Those at the scene, All did agree, That the slayer who
ran, Looked a lot like me”.
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