Dependent Facts
Facts are dependent when the probability that one fact, Fact A, is true, is
dependent on the probability that another fact, Fact B, is true. In the simple
case this
means that the facts go together. Then the probability that any
specific fact is true, for example Fact A, is the same as the probability for any
other specific fact, for example Fact B. This is also the probability that the
facts, taken together as an overall version of the facts (in the example Facts A
and B), are true.
To illustrate this using the example above (where the plaintiff has to prove
Facts 1-4 to satisfy Elements 1-4 of a cause of action) we assume that Facts
1and 2 are dependent. Thus is the probability of one being true is 35% that is
also the probability that the other is true.
Several Versions
Introduction
Here we consider the case where there are two or more versions of the overall
facts in a case. For example, there is a plaintiff and a defendant, and there are
four overall versions of the facts, Version Pa, Version Pb, Version Pc and
Version D. These overall versions support the parties in the following way:
Plaintiff
Version Pa, Version Pb and Version Pc support the Plaintiff
Defendant
Version D supports the Defendant
Figure 24.3 Two of More Overall Versions
In this situation, for any party with more than one overall version of the facts in
their favour the court has to take the probability that each version of the facts
is true and work out from these the probability that the party has made out
their case.
To calculate the probability that a party has made out their case the court
should use the addition rule. It takes the probability for each overall version for
the plaintiff or defendant and adds them. So, if there are three versions and the
probabilities are X%, Y%, and Z% the probability for that party’s case is
(X+Y+Z)%.
Let us illustrate this using a very extreme but illustrative case, where there are
seven versions. Here, Versions 1-3 favour the plaintiff and Versions 4-7 favour
the defendant. The probabilities of Versions 1, 2 and 3 are 30%, 5% and 20%,
and the probabilities of Versions 4, 5, 6 and 7 are 15%, 10%, 15% and 5%.
We can set out the calculations in the following table:
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