This is an extract from writing dealing with induction as a means of proof.
Objective Probability
Objective probability is also called classical probability. It is properly used in a
situation where events happen randomly so that every outcome is equally
likely. In these circumstances evidence for or against any outcome is
symmetrical in that it favours no specific outcome. Examples are spinning a
roulette wheel, throwing dice and drawing cards from a deck. For this reason
there will be few opportunities where it can be properly used in cases.
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Dealing Cards
To illustrate objective probability, assume that two cards are drawn in
succession from a standard and well shuffled deck of 52 cards, and each was
an ace. Assume that there is no other evidence of the state of the deck of
cards, the probability of this
happening based on classical probability is as
follows:
Action
Probability
Action 1: An ace on the first draw
4/52
Action 2: An ace on the second draw
3/51
Action 1 and Action 2 (4/52 x 3/51)
0.005 [approximately]
Figure 23.1 Illustration of Classical Probability
Thus based on classical probability the probability of both Action 1 and
Action 2 is the multiple of their individual probabilities. This comes to
0.0045248 which is approximately 0.005. This constitutes 5 chances in
100,000, which equals 1 chance in 20,000.
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Corroboration
The judge said son, what’s your alibi,
If you were somewhere else, then you won’t have to die.
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Corroboration is invoked on the basis that evidence is stronger when it is
corroborated, that is, it is supported by another
piece of evidence.
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For
example, witness A says that she saw X happen and witness B says much the
same thing. Furthermore, evidence is even stronger if these witnesses are
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Christopher Enright Legal Reasoning Chapter 9 Probability
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Examples are Tenax v Steamship Co v The Brimnes
[1975] QB 929 Rose v
Orchard Investments
[87] Aust Torts Reports ¶80-121 and Rogers v Whitaker
(1992)
109 ALR 625, where the probability of an operation failing was 1 in 14,000.
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M Wilkens, D Dill Long Black Veil, originally recorded by Johnny R Cash on
12 July 1964.
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Devries v Australian National Railways Commission
(1993) 177 CLR 472, 479,
112 ALR 641, 645-646.
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