  Although researchers have found evidence contextual bias in forensic science,
the discussion of contextual bias is currently qualitative. We formalize years
of empirical research and extend this research by showing quantitatively how
biases can be propagated throughout the legal system, all the way up to the
final determination of guilt in a criminal trial. We provide a probabilistic
framework for describing how information is updated in a forensic analysis
setting by using the ratio form of Bayes' rule. We analyze results from
empirical studies using our framework and use simulations to demonstrate how
bias can be compounded where experiments do not exist. We find that even minor
biases in the earlier stages of forensic analysis lead to large, compounded
biases in the final determination of guilt in a criminal trial.
