Technical findings established arson in some cases, but no hard evidence directly linked the defendant to the crimes. Probabilistic analysis was used to determine whether these findings indicated that the firefighter had to be the arsonist, while taking into account special features that could explain the peculiar behavior of the defendant. The main goal of the analysis was to organize, structure, and reduce the material to a few quantities that were easier to understand than the problem in its original form. The court accepted the relevance of the calculations and used it against the defendant, but little corroborating evidence existed, and the defendant was acquitted. However, the analysis did reduce the problem to a few intelligible key conditions, creating a better basis for argument and decisionmaking than would otherwise be possible. Table, figure, and 8 references (Author abstract modified)