Duty of Impartiality
Definition
The obligation that an expert witness owes to the court rather than to the party that retained them. Codified in England and Wales by CPR Practice Direction 35; reflected in the BSA 2023 and analogous rules in other jurisdictions. Breach of this duty can ground sanctions, adverse costs orders, or exclusion of the evidence.
- Owed to
- The court, not the retaining party
- England & Wales basis
- CPR Practice Direction 35
- Also reflected in
- CrimPR Part 19 (criminal proceedings, E&W)
- Breach consequence
- Sanctions, costs orders, or exclusion
Common questions
How does the duty of impartiality differ from simply being honest?+
It goes beyond not lying: an expert must actively present balanced conclusions, disclose facts that undermine their opinion, and avoid becoming an advocate for the party paying them, even when that party would prefer a more favourable framing.
What typically triggers a court finding that an expert breached this duty?+
Common triggers include omitting contrary evidence or literature from a report, straying outside one's area of competence, or communicating with instructing solicitors in a way that shapes conclusions rather than simply clarifying instructions.
Related terms
- 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...
- Daubert Standard
- The US federal evidentiary standard (Daubert v. Merrell Dow Pharmaceuticals, 1993) requiring that expert testimony be based on scientifically valid methods with...
- Fabrication of Evidence
- The deliberate creation of false scientific results or the falsification of existing results for use in legal proceedings. It is the most...
- Factual Section vs Interpretation Section
- A structural distinction in expert reports between what was observed (verifiable facts, not requiring expert judgment) and what those observations mean (expert...
- Frye Standard
- The US legal test for admissibility of scientific evidence, originating from Frye v. United States (1923), which required that a technique be...
- 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...
- 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,...
- 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...
- Witness Immunity
- A common-law protection that historically shielded expert witnesses from civil liability for statements made in judicial proceedings. In England and Wales it...
- Wrongful Conviction Review
- A post-conviction process in which a court, review commission, or independent body re-examines the evidence supporting a conviction. In England and Wales...
Explained in these topics
- Expert Liability, Bias and Misconduct
- Expert Reporting and Court Testimony in Forensic BotanyThe expert's overriding obligation to the court, not to the retaining party. An expert must present findings fairly, including findings that favour the opposin...