6 When science meets law

Increasingly, scientific evidence is being presented in a mathematical form based on a formula first articulated by the Reverend Thomas Bayes, an amateur mathematician, which was presented to the Royal Society in 1763, after his death. This approach is sometimes called ‘Bayesianism’, ‘the Bayesian approach’, or ‘Bayes’ Rule’. The Bayesian approach is that it is generally accepted to be the only logical method of combining different probabilities. Yet Bayesianism has created a significant problem for law courts because very few lawyers or laypeople think in such mathematical terms. This section will briefly introduce Bayesianism before discussing how the courts have tried to accommodate it.

• 1 R v Denis Adams (No 1) [1996] 2 Cr. App. R. 467.
• 2 R v T [2011] 1 Cr. App. R. 9 (CA).