The effect of contextual information on decision-making in forensic toxicology

The impact of cognitive bias on decisions in forensic science has been demonstrated in numerous disciplines such as DNA and fingerprints, but has not been empirically investigated in the more objective domains, such as forensic toxicology. In the first experiment, participants (n = 58) were affected by irrelevant case information when analysing data from an immunoassay test for opiate-type drugs. In the second experiment, participants (n = 53) were biased in their choice of tests, for example, the age of the deceased impacted testing strategy: for older people, medicinal drugs were commonly chosen, whereas for younger people drugs of abuse were selected. Based on the results that examiners analyzing case data may have biases if they are given access to case context, we propose that examiners analysing presumptive test data are blind to irrelevant contextual information. Furthermore, that forensic toxicology laboratories use a consistent protocol for selecting tests, and that any deviations are documented and justified.