After Sally Clark was found guilty, the Royal Statistical Society issued a statement saying that there was “no statistical basis” for the expert’s claim. They expressed concern at the “misuse of...

After Sally Clark was found guilty, the Royal Statistical Society issued a statement saying that there was “no statistical basis” for the expert’s claim. They expressed concern at the “misuse of statistics in the courts”. Eventually, Sally Clark was acquitted in June 2003. What did the expert miss?

A. He made an arithmetic error.

B. He made two mistakes. First, he misused the multiplicative rule and did not take into account how rare it is for a mother to murder her children. After using Bayes’ rule, we found a probability closer to 0.5 than 1 in 73 million.

C. He mixed up the numerator and denominator of Bayes’ rule.

D. He did not use R.