The paper explores the use of statistical data and statistical assumptions as evidence in criminal trials. It is suggested that a finding of guilt includes not only its main factual proposition but also additional propositions that support and affirm it. Specifically, it includes not only the proposition that the defendant committed the offence but also the additional affirming proposition that it is this defendant rather than any other potential defendant who committed the offence (the ‘D rather than A’ proposition). Some statistical generalisations provide reasons in defence of the main proposition but not in defence of the affirming proposition, which then remains random or arbitrary. Yet since criminal convictions include a moral judgement, they cannot be justified where some of their propositions are arbitrary. Accordingly, such statistical generalisations cannot justify a criminal conviction.
