​KembaraXtra – Indian Evidence Law – Bharatiya Sakshya Adhiniyam – Facts Bearing upon Opinions of Experts (Section 40)
1. Basic Principle of Section 40Under Section 40 of the Bharatiya Sakshya Adhiniyam, the law provides that:
Facts which are otherwise not relevant may become relevant if they support or are inconsistent with the opinion of an expert, provided that such expert opinion itself is relevant.
This provision highlights an important exception to the general rule of evidence--
👉 Irrelevance is not absolute; certain facts gain relevance when connected to expert opinion.

2. Core Concept of the SectionOrdinarily, the law excludes collateral or indirect facts from consideration. However, when expert opinion is involved, such facts may be admitted if they:

• Corroborate (support) the expert’s opinion, or
• Contradict (challenge) the expert’s conclusion

Thus, the section ensures that expert opinions are not accepted blindly but are tested against supporting or opposing factual circumstances.

3. Nature of Such Facts (Res Inter Alios Acta)This section deals with what is known as:
👉 Res inter alios acta (transactions or facts between others)
Normally, such collateral facts are excluded because they do not directly relate to the issue in dispute. However, Section 40 creates an exception where:

• The issue involves scientific, technical, or specialized matters, and
• The collateral facts help to illustrate, support, or disprove expert opinion

4. Illustrations Explained(a) Poisoning Case

• Issue: Whether A was poisoned by a particular substance
• Relevant fact: Other individuals poisoned by the same substance showed certain symptoms

If experts confirm or deny that these symptoms are typical of that poison, such facts:

• Help in evaluating the expert’s opinion
• Become relevant under this section

(b) Harbour Obstruction Case

• Issue: Whether a seawall caused blockage of a harbour
• Relevant fact: Other similar harbours without seawalls were also obstructed around the same time

This suggests:

• The obstruction might not be due to the seawall
• Such comparative facts can support or contradict expert engineering opinions

This principle has its roots in English law, where courts admitted similar comparative evidence to assess expert conclusions.

5. Scope and ApplicationThis section applies when:

1. Expert opinion is relevant and has been presented, and
2. Additional facts are introduced to:
   • Support the opinion, or
   • Show inconsistency in the opinion

Key Idea👉 Expert opinion must be tested against real-world facts and comparable situations to determine its reliability.

6. Role of Expert EvidenceExpert opinions are typically based on:

• Scientific analysis
• Technical expertise
• Experiments and observations

However, such opinions are not conclusive proof. Section 40 ensures that:

• Experts can be supported by corroborative facts, or
• Their opinions can be discredited through contradictory facts

This strengthens the fairness and objectivity of judicial decisions.

7. Evidentiary ValueThe importance of such supporting or contradicting facts depends on:

• Their logical connection with the expert opinion
• Their similarity to the facts in issue
• Their ability to strengthen or weaken the expert’s reasoning

The court evaluates whether these facts genuinely assist in determining the correctness of the expert’s conclusion.

8. Key Takeaways

• Section 40 allows otherwise irrelevant facts to become relevant when linked to expert opinions.
• Such facts may:
  • Support, or
  • Contradict expert conclusions
• It is an exception to the rule excluding collateral facts.
• It is especially important in scientific and technical cases.
• The aim is to ensure that expert opinions are properly tested and not blindly accepted.

In One Line👉 Facts that support or challenge expert opinion become relevant, even if they are otherwise unrelated.