Validation Study
Definition
An empirical study that tests the accuracy, precision, and error rate of a forensic method under realistic conditions. Validation data are required to support the reliability of any probabilistic statement made using that method in court.
- Measures
- Accuracy, precision, error rate
- Conditions
- Realistic, casework-representative conditions
- Legal role
- Supports probabilistic statements made in court
- Relation to Daubert
- Addresses known/potential error rate factor
Common questions
How does a defense attorney typically challenge expert testimony using validation data?+
Cross-examination often probes whether the validation study's sample types and conditions actually match the casework sample at issue, since a method validated only on fresh, high-quality samples may not support the same confidence level applied to a degraded or low-quantity exhibit.
Who typically conducts a validation study for a new forensic technique?+
It is usually done by the method's developer, an academic research group, or a professional working group, and published or peer-reviewed so that individual laboratories can then verify the method locally before adopting it.
Related terms
- Bayes' Theorem
- The mathematical rule that relates prior odds, the likelihood ratio, and posterior odds. In the odds form: O(Hp|E) = O(Hp) x LR....
- Evaluative Reporting
- A framework for expressing forensic conclusions in terms of the probability of the evidence given the prosecution hypothesis versus the defence hypothesis...
- Likelihood Ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- Prosecutor's Fallacy
- The error of treating the RMP (or its reciprocal) as the probability that the defendant is innocent, or as the probability that...
- Random Match Probability (RMP)
- The probability that a randomly chosen unrelated person from the relevant population would match the evidence profile by chance. A very small...