Plaintiff’s Versions
Probability
Total
Version 1
30%
Version 2
5%
Version 3
20%
Total
55%
Defendant’s Versions
Version 4
15%
Version 5
10%
Version 6
15%
Version 7
5%
Total
45%
Overall Total
100%
Figure 24.4 Several Overall Versions of Facts
In this case we can add together the probabilities of all the versions favouring each
party
to
give
the
probability
of
that
the
party
has
made
out
their
case.
Here
the
plaintiff’s case is 55% probable and the defendant’s case is 45% probable.
Let us see what this means in practical terms. Assume that the plaintiff is suing
the defendant for negligence. The plaintiff claims that the defendant sold her a
car and the car leaks oil. Subsequent to the sale the defendant has also
serviced
the plaintiff’s car. It was after this service that the leaking of the oil
was first observed.
The issue then is whether the car got this way through the fault of the
defendant. To show this, there could be the following possibilities (which need
to be proved by inference):
(1)
The leak was caused by the defendant putting a defective part in the car
while servicing it. This has a probability of X%.
(2)
The leak was caused by the defendant not properly tightening certain
nuts while servicing the car. This has a probability of Y%.
(3)
The leak was deliberately caused during a service of the car by a
disaffected employee of the defendant who did it to spite the defendant. This
has a probability of Z%.
Any of these versions of the facts provides an explanation for how the
defendant was responsible for the leak. Hence the probability of the plaintiff’s
case being true is the probability that any one of these versions happened. The
probability of this is the sum of the individual probabilities, ie (X + Y + Z)%.
Thus, if X = 25, Y = 15 and Z = 12, the probability that the plaintiff’s case is
true is (25 + 15 + 12)%, namely 52%.
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