Uses
Introduction
There are two uses of probability which are of fundamental importance to
working with law. One arises in using policy to make law, while the other is
located in the task of finding facts.
Making Law
Probability is deployed in the process of making legislative policy. Any law is
essentially trying to change the future. Consequently as part of the process of
making of law it is necessary to know what effects a proposed law is likely to
cause. This invokes probability in two ways.
First, to identify the effects that a law will cause, it is necessary to invoke laws
of behavioural science.
These are derived using an experimental process that
frequently relies on statistical inferences. Statistical inferences are based on
probability.
Second, even if a causal law suggests that a proposed statute might cause a
particular effect, there may be
some uncertainty. Since probability is a means
of encapsulating uncertainty surrounding future events, it can be used to factor
this uncertainty into the tasks of making and interpreting a law.
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Finding Facts
Probability is used by courts in the process of finding facts as a means of
coping with the uncertainty that is so often inherent in the task. Probability is a
way of encapsulating and working with uncertain knowledge.
There are two strands to this uncertainty. First, in many cases, and arguably in
all cases, it is not possible for a decision maker such as a court to be
absolutely convinced as to the truth of past events.
Second, this inherent uncertainty is legally recognised and captured in the rules
depicting the standard of proof (or the standard of truth as it is also called in
this discussion). Thus, for a party to win their case the court does not have to
be absolutely convinced that it is true beyond any doubt whatsoever. Instead a
party has to prove their case according to the level or degree of certainty
prescribed by the legal rules for the standard of proof.
While each jurisdiction can create its own standard of proof by statute, the
common law standards are generally used. For a civil case the common law
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Chapter 15 Cause: Responding to Uncertainty. This explains how one way
of coping with uncertainty consists of expected value. Expected value is
discussed later in this chapter.
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