Evaluative Reporting
Definition
A framework for expressing forensic conclusions in terms of the probability of the evidence given the prosecution hypothesis versus the defence hypothesis (likelihood ratio); endorsed by ENFSI as a bias-mitigation measure alongside contextual controls, because probabilistic language permits formal expression of uncertainty.
- Also known as
- Likelihood ratio reporting, probabilistic reporting
- Key standards that endorse it
- ENFSI (European Network of Forensic Science Institutes) and UK FSR Codes of Practice
- Common alternative formats
- Graduated verbal scales like 'strong support' or 'moderate support' instead of numerical ratios
Common questions
Why use likelihood ratios instead of saying 'match' or 'no match'?+
Likelihood ratios express forensic conclusions probabilistically rather than as categorical yes/no statements. This permits a formal expression of uncertainty and is endorsed by ENFSI as a bias-mitigation measure because it prevents overconfidence in forensic opinions.
What does a likelihood ratio actually mean?+
It shows how many times more probable the evidence is under the prosecution's hypothesis than under the defence's hypothesis. For example, a likelihood ratio of 100 means the evidence is 100 times more consistent with the prosecution's version of events than with the defence's.
Is evaluative reporting mandatory in forensic labs?+
Standards vary by jurisdiction. The UK FSR Codes of Practice and ENFSI require it, including for fingerprint identification. In the US, it is not yet mandated across all practices.
Related terms
- 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...
- 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....
- 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...
- Blind Verification
- The procedure in which a second fingerprint examiner independently performs the Analysis and Comparison stages without knowledge of the first examiner's conclusion....
- Confirmation Bias
- The cognitive tendency to search for, interpret, favour, and recall information in a way that confirms or supports one's prior beliefs or...
- Contextual Bias
- The influence of case-relevant background information (suspect financial difficulties, police intelligence) on the direction of an examiner's technical analysis. Demonstrated experimentally for...
- Linear ACE-V
- An implementation of ACE-V methodology that enforces strict sequential documentation: analysis of the latent mark must be completed and recorded before the...
- Posterior Odds
- The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis after the forensic evidence is taken...
- Prior Odds
- The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis before the forensic evidence in question...
- Sequential Unmasking
- An information-sequencing protocol in which the examiner receives the questioned material first, completes and documents the analysis before receiving the known standards,...
- SWGFAST
- Scientific Working Group for Friction Ridge Analysis, Study and Technology; the predecessor body to the OSAC Friction Ridge Subcommittee; produced documentation standards...
Explained in these topics
- ACE-V Methodology and the Brandon Mayfield Madrid Bombing ErrorA reporting framework in which a fingerprint identification opinion is expressed as a likelihood ratio or a graduated verbal scale (e.g. strong support, modera...
- Dror 2006 Cognitive Bias and the Bias-Mitigation ToolkitA framework for expressing forensic conclusions in terms of the probability of the evidence given the prosecution hypothesis versus the defence hypothesis (lik...
- Expert Testimony and the 2009 NAS Critique of Fingerprint IDA framework for expressing forensic conclusions in terms of the probability of the evidence given competing hypotheses (identification vs. coincidental match),...
- Interpreting Biological Evidence in CourtA reporting style in which the expert states findings in terms of competing hypotheses and their relative probabilities, rather than simply reporting a match o...
- The Likelihood Ratio: Definition and LogicA reporting framework in which the forensic expert states the probability of the evidence under each competing hypothesis, or their ratio, rather than stating...
- How Numbers Enter Forensic ConclusionsA framework for forensic expert evidence in which the examiner states the probability of the findings under each competing proposition rather than asserting a...
- Prior and Posterior Odds in CourtThe style of expert testimony in which the scientist reports the LR (or a verbal equivalent) rather than stating a probability of the source proposition being...
- Quality Systems: ISO 17025, NABL, ANAB, UKAS and Proficiency TestingA reporting style endorsed by the FSR Codes of Practice in which the forensic examiner frames the significance of evidence as a likelihood ratio (LR): how many...
- The Role of Statistics in Evidence EvaluationA reporting framework in which the forensic scientist states a pair of propositions, assigns a likelihood ratio or verbal equivalent representing the evidentia...