ENFSI Guideline for Evaluative Reporting
Definition
A consensus guidance document from the European Network of Forensic Science Institutes that defines how member laboratories should express evaluative opinions. It mandates proposition-based reasoning, likelihood ratio expression, and a standardised verbal scale, and prohibits source-attribution conclusions.
- Issuing body
- European Network of Forensic Science Institutes
- Core requirement
- Proposition-based reasoning
- Reporting format
- Likelihood ratio with a standardised verbal scale
- Prohibits
- Source-attribution conclusions
Common questions
Why does the guideline prohibit experts from stating a definite source attribution?+
A flat statement that a mark came from a specific person overstates what the underlying statistics support. The guideline requires the expert to weigh the evidence under competing propositions instead, leaving the final decision on identity to the court.
What is proposition-based reasoning in practice?+
The expert evaluates the evidence against at least two competing explanations, typically one favouring the prosecution and one favouring the defence, and reports how much more likely the findings are under one proposition than the other.
Related terms
- Verbal Scale
- The ENFSI translation of numerical likelihood ratios into courtroom language: very strong support (LR over 10,000), strong support (LR 1,000-10,000), moderate support...
- Accreditation Body
- A national or regional organisation that assesses laboratories against ISO/IEC 17025 and grants accreditation. Examples include UKAS (United Kingdom Accreditation Service), NIST-associated...
- Evaluative Conclusion
- A forensic opinion that addresses the weight of the evidence, typically expressed as an LR or a verbal equivalent. Distinct from a...
- ILAC G19
- A guidance document from the International Laboratory Accreditation Cooperation on the use of uncertainty of measurement in forensic science reporting. It requires...
- ISO 17025
- International standard for the general requirements for the competence of testing and calibration laboratories. Covers management system requirements (document control, internal audits,...
- 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...
- Proposition Pair
- The two competing hypotheses that frame an evaluative opinion: typically a prosecution proposition (Hp) and a defence proposition (Hd). A compliant report...
- Source-Level Hypothesis
- A proposition about who or what produced a trace, for example 'this glass came from the broken window at the crime scene'...
- UK Forensic Science Regulator (FSR)
- The statutory body in England and Wales responsible for setting and monitoring quality standards in forensic science. The FSR has published codes...
Explained in these topics
- Evaluative Opinion Standards and Frameworks
- Verbal Equivalents of the Likelihood RatioA 2015 document from the European Network of Forensic Science Institutes that sets out best practice for Bayesian evaluative reporting, including a recommended...