probability of 95% and 5%, and how little difference there is between a
probability of 50% and a probability of 51%.
Third, and this is the major reason, many of the processes in finding facts
involve using specific probabilities to calculate a further probability and using
this further probability to continue the process. Obviously if probability is not
expressed in numbers it is not possible to do these calculations. Of course it
would be possible to apply the logic of the calculations to verbal expressions
of probability, but
this would be clumsy, especially compared to the
calculations that perform the process so easily.
Two Stages
Introduction
Step 2 has two stages:
(1)
Specific Facts. Here the court assesses the probability that each specific
piece of fact given in evidence is true.
(2)
Overall Facts. Here the court assesses the probability that the overall
version of the facts, representing a party’s case, is true.
Stage 1: Specific Facts
Typically particular pieces of evidence seek to prove some of the specific
facts that make up a party’s case. The court needs to estimate the probability
that these specific facts are true. How a court assesses the probability that
specific pieces of facts are true depends on the means by which parties seek
to prove facts:
(1)
Deeming Provisions. The effect of a deeming provision is that the court
has to treat the relevant fact as true. Consequently the court does not have to
make any independent assessment of the facts. It just accepts them as true.
(3)
Observation. Where evidence is based on observation by the judge the
judge assesses how good their own observation is. Where evidence is based
on observation by a witness, the court uses two methods to assess its truth. It
may use cognitive science (as the court understands it) to measure the
reliability of the observation. It may also use induction –
does the evidence
describe things happening in the way one would expect them to happen.
(2)
Induction. Induction can be used on its own where there is no
observational evidence of facts (no one saw or heard anything), or it can be
used in conjunction with observational evidence. In simple terms induction is
concerned in this context with how things usually happen. Assume that X, Y
and X often happen together. Then in a particular case it is clear that X and Z
have happened but there is no direct evidence that Y also happened. In this
case the court can reason inductively to conclude that Y has happened in this
case. The probability of Y happening determines the strength of the argument
that Y has happened.
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