Defense attorney's fallacy

Biological Parallel

Defense attorney's fallacy: 'Eyewitness accuracy is only 80%, therefore 20% chance client is innocent.' But if prior probability of guilt (given other evidence) is 95%, posterior probability remains >99% even with imperfect testimony. Prey animals illustrate correct Bayesian updating: if a meerkat sentry identifies eagle-shape overhead (80% reliable given visual limitations) and prior probability of eagle presence is high (soaring observed minutes earlier, alarm calls from neighboring colonies), the group flees despite signal imperfection. Ignoring priors is fatal in predator-prey dynamics. Businesses make inverse errors: dismissing valuable-but-noisy signals (customer complaints at 70% accuracy) when base rates make them highly informative, rejecting candidates with 85% assessment validity because 'not perfect,' ignoring leading indicators with 75% predictive power.