activities are the subject of the field of study known as cognitive science. Thus
in a formal sense it is the key to assessing the probability that evidence from a
witness is true.
Unfortunately, like most fields of study, cognitive science cannot explain
everything. To the extent that science has not been able to provide acceptable
explanations it is necessary for courts to work things out as best they can. In
doing this they may, explicitly or implicitly, rely on some assumptions that are
not scientifically validated. These assumptions can come, directly or indirectly,
from a number of sources. They
may be conventional perception,
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experience, hunch, intuition, folklore, folk psychology, common sense and
received wisdom.
580
While these assumptions may be received from others, a legislature or court
uses them only if they reflect their own perception of how things ordinarily
happen in the world. Since a view of how the world works obtained from
these sources is not scientifically based it is obviously not necessarily reliable.
For this reason, using assumption can easily get it wrong. Getting it wrong
can, for example, introduce false stereotypes and prejudice into the process of
finding facts.
It would, however, take a very complicated model to explain the process of
estimating the probability that specific facts are true based on observation.
Therefore in this section the best that can be done is to sketch in outline the
form that such a model might take. This model is based on two theorems,
Evidentiary Theorem 1 and Evidentiary Theorem 2.
Evidentiary Theorem 1
Theorem 1 says that a witness is telling the truth - that is the full or complete or
whole truth and the totally accurate truth - when three conditions are satisfied:
#
Condition 1: The witness has fully observed the facts.
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Condition 2: The witness has accurately remembered the facts.
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Condition 3: The witness has truthfully recounted the facts.
When the conditions of truth are satisfied the witness must be telling the truth.
And the only other reason that a witness is telling the truth is a pure fluke,
which is so highly unlikely that we can dismiss it for the purposes of this
simple model.
This proposition, that the presence of these conditions leads to the truth, can
be used in two ways. First, when we know for certain that this causal law
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Neat Holdings v Karajan Holdings (1992) 67 ALJR 170 at 170-171, and see also
Briginshaw v Briginshaw (1938) 60 CLR 336 at 361-362
580
Hodgson (1995) p 738
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