that X and Z happened, it may find by induction (or inference as courts are
wont to call it) from X and Z that Y happened.
In theory, courts could insist that facts must be shown to be absolutely true to
be proved. This, however, would be unrealistic. Instead courts adopt an
abductive approach and require that facts be proved according to some
stipulated level of probability. This is described in law as the standard of
proof. Two common standards are the preponderance of evidence or balance
of probabilities that involves proof that is 51% probable and the standard of
proof for criminal cases which is proof beyond reasonable doubt (for which
there is no agreed numerical measure). Logically there are three steps in finding
facts, which will now be outlined.
Step 1: Versions of Truth
The court gathers the various versions of the facts.
Step 2: Probability of Truth
This is the key step. There are two parts:
(i)
Assessment of Evidence. The first part involves assessment of
individual pieces of evidence. Here two major types of consideration are
mentioned:
(A)
Patterns of Behaviour. Patterns of behaviour may occur
because of some custom or social practice. They can also occur because they
represent a rational way of doing things. Assume that A, B and C at least
sometimes occur together. A court finds that A and C happened and
something happened after A and before C. In this situation the court may
argue by induction that the pattern of A, B and C has repeated itself. On this
basis it finds that B occurred and did so after A and before C.
(B)
Observation by a Witness. A court assesses the probability
that evidence of their observations given by a witness is true by two means. (a)
Courts use cognitive science to assess the accuracy of the initial observation,
the soundness of the witness’ memory and the truthfulness of the witness’s
account of the relevant events.
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Since cognitive science is not fully developed
courts inevitably have to rely on “laws” that do not have a proper scientific
basis. This comes down to such things as common sense and guesswork. (b)
Courts also assess the probability that individual facts are true by inductive
reasoning relying on how things commonly occur because of social practices
or good reason.
(ii)
Assessment of Party’s Case. The second part involves
assessment of a party’s overall case, which is composed of a number of
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There are two theorems, Evidentiary Theorem 1 and 2 that can guide a court in
the task of assessing the probability that observation by a witness is true by reference to
cognitive science. See Chapter 31 Model for Using Law.
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