Bharatiya Sakshya Adhiniyam, 2023
Section 45
Grounds of opinion, when relevant
Whenever the opinion of any living person is relevant, the grounds on which such opinion is based are also relevant.
Illustration. An expert may give an account of experiments performed by him for the purpose of forming his opinion. Character when relevant
Why this exists
Courts often rely on expert opinions (from doctors, scientists, handwriting analysts, etc.) under other provisions dealing with expert evidence. But an opinion alone, without knowing how it was formed, can be hard to trust or challenge. This provision, inherited from Section 51 of the Indian Evidence Act, 1872 (a law shaped by 19th-century British-Indian legal drafting influenced by common law principles), ensures that the reasoning, data, and methods behind an opinion are open to scrutiny, so that both the court and the opposing party can test the opinion's reliability rather than accepting it blindly.
How courts read it
Under the predecessor provision (Section 51 of the Evidence Act, 1872), Indian courts have consistently held that an expert's bare opinion carries little weight unless the underlying data, methodology, and reasoning are disclosed and can be examined. Courts have used this principle to allow cross-examination of experts on their methods, and to discount opinions where the expert could not explain or justify the basis of their conclusion.
Common misconceptions
- Myth: An expert's opinion must be accepted just because they are an expert.
Fact: Courts can and do examine the reasoning and evidence behind an expert's opinion; the opinion alone is not automatically conclusive. - Myth: This section only applies to scientific experts.
Fact: It applies whenever any living person's opinion is relevant under the law, not just to scientific or technical experts.