ILAC G19
Definition
A guidance document from the International Laboratory Accreditation Cooperation on the use of uncertainty of measurement in forensic science reporting. It requires laboratories to estimate and report measurement uncertainty alongside evaluative opinions, linking this to ISO 17025 accreditation.
- Issuing body
- International Laboratory Accreditation Cooperation
- Subject
- Measurement uncertainty in forensic reporting
- Requirement
- Estimate and report uncertainty alongside evaluative opinions
- Linked to
- ISO 17025 accreditation
Common questions
Why does a forensic report need a stated measurement uncertainty at all?+
Any quantitative forensic measurement, such as a blood alcohol concentration or a drug purity figure, carries some margin of error from instrument calibration, sampling, and method limits. Reporting that uncertainty lets a court judge how much weight the number can bear rather than treating it as an exact figure.
How does ILAC G19 connect to a lab's ISO 17025 accreditation status?+
ISO 17025 requires accredited laboratories to demonstrate competence in estimating measurement uncertainty. ILAC G19 gives forensic laboratories specific guidance on applying that general requirement to evaluative opinions, so accreditation bodies use it when assessing compliance.
Related terms
- 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...
- ENFSI Guideline for Evaluative Reporting
- A consensus guidance document from the European Network of Forensic Science Institutes that defines how member laboratories should express evaluative opinions. It...
- ISO 17025
- International standard for the general requirements for the competence of testing and calibration laboratories. Covers management system requirements (document control, internal audits,...
- Proposition Pair
- The two competing hypotheses that frame an evaluative opinion: typically a prosecution proposition (Hp) and a defence proposition (Hd). A compliant report...
- 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...