Should criminal trials use the rarity of a natural cause as evidence of causation?

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When a litigant must prove that a result was caused in a particular way, it may seem compelling to cite the extremely low probability that it arose from an alternative natural cause. Contrary to that intuition, the author argues that statistical evidence of an alternative cause’s extremely low probability should not affect the claim that a particular cause produced the result.

The author argues that the low probability of a natural cause is relevant to the case only if contrasted with another statistic: the frequency of the criminal activity among people similar to the accused. Connecting probabilistic generalisations in legal fact-finding with the issue of free will, the author argues that comparing frequencies this way in criminal law is objectionable as a matter of principle, regardless of how reliable the statistical analysis is.

The article concludes that, if the low probability of a natural cause has probative value only when compared with a statistic that is objectionable, neither piece of evidence should be admitted in criminal trials.