Basis of Opinion
Definition
The underlying data, facts, or methodology on which an expert opinion rests. Courts require disclosure of the basis so the opposing party can challenge it through cross-examination or counter-expertise.
- Field
- Expert / opinion evidence
- Definition
- Data, facts, or methodology behind an expert opinion
- Requirement
- Disclosure to the opposing party
- Purpose
- Enables cross-examination and counter-expertise
Common questions
What happens if an expert refuses to disclose the basis of an opinion?+
Courts generally treat an undisclosed basis as grounds to exclude or heavily discount the opinion, since an opposing party cannot meaningfully test a conclusion it cannot see the reasoning behind. Full disclosure is usually a precondition for the opinion being admitted at all.
Does disclosing the basis of opinion mean handing over raw case notes?+
It generally means the underlying data, methods, and reasoning the expert relied on, which in practice often does include notes, worksheets, and validation records, since a challenge to methodology needs to see exactly what was done, not just the final stated conclusion.
Related terms
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- Opinion Evidence
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- Overriding Duty to the Court
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- Section 45, Bharatiya Sakshya Adhiniyam 2023
- The Indian statutory provision permitting courts to consider the opinion of persons specially skilled in foreign law, science, art, handwriting, or finger...
- Ultimate-Issue Rule
- The traditional prohibition on an expert stating an opinion on the very factual question the court must decide, on the ground that...