Expert Opinion and Hostile Witnesses Under the BSA

Under the Bharatiya Sakshya Adhiniyam, 2023 (BSA), the opinion of an expert is a relevant fact only when the court must form an opinion on foreign law, science, art, handwriting, finger impressions or electronic records (Section 39), and the court still decides the question itself. A "hostile witness" is not a phrase the Act uses: the BSA lets the court, in its discretion, allow a party to cross-examine its own witness (Section 157), and the parts of that witness's evidence which remain reliable can still be used. Both rules carry over the old Evidence Act position with new section numbers.

This explainer is for B.A. LL.B. and LL.B. students preparing for the evidence paper, and for anyone who has read a news report saying that "the witness turned hostile" and wondered whether the case is over. It is not over, and knowing why is a good test of whether you understand how a trial actually works.

Which sections of the BSA apply?

The BSA replaced the Indian Evidence Act, 1872 from 1 July 2024. The provisions you need are grouped in two places. The old Evidence Act numbers are given in brackets only as pointers for reading older judgments.

• Section 39 (old Section 45): opinions of experts, including the Examiner of Electronic Evidence.
• Section 40 (old Section 46): facts that support or are inconsistent with expert opinions.
• Section 41 (old Section 47): opinion of a person acquainted with someone's handwriting, and of a Certifying Authority on an electronic signature.
• Section 45 (old Section 51): when an opinion is relevant, the grounds for it are also relevant.
• Section 148 (old Section 145): cross-examination as to previous statements in writing.
• Section 157 (old Section 154): question by party to his own witness.
• Section 158 (old Section 155): impeaching the credit of a witness.

Two provisions of the Bharatiya Nagarik Suraksha Sanhita, 2023 (BNSS) sit next to these in criminal trials: Section 181 on the use of statements made to the police, and Section 329 on reports of certain government scientific experts.

Who is an expert under Section 39?

Section 39(1) says that when the court has to form an opinion on a point of foreign law, science or art, or any other field, or as to identity of handwriting or finger impressions, the opinions of persons "specially skilled" in that field are relevant facts. Such persons are called experts. The illustrations in the Act give the classic examples: whether a person died of poison, whether an accused was of unsound mind, and whether two documents were written by the same hand.

Section 39(2) is the newer part. Where the court must form an opinion on information stored or transmitted in a computer resource or other electronic or digital form, the opinion of the Examiner of Electronic Evidence referred to in Section 79A of the Information Technology Act, 2000 is relevant, and the Explanation says that such an Examiner "shall be an expert". This matters in cyber fraud cases and in disputes built on chat messages, call records or CCTV footage, where the question is often whether the data was altered.

Keep three supporting rules in mind:

1. Section 40: facts that are not otherwise relevant become relevant if they support or contradict an expert's opinion. A second laboratory report pointing the other way is a good example.
2. Section 41: a lay person can give an opinion on handwriting if they know it. The Explanation lists three ways of knowing: having seen the person write, having received replies from that person, or having had that person's documents placed before them in the ordinary course of business. So a bank clerk in Nagercoil who has handled a customer's cheques for years can speak to the signature without being a handwriting expert.
3. Section 45: the grounds of an opinion are also relevant. An expert who gives a bare conclusion without reasons gives the court very little to work with.

How much weight does a court give to expert opinion?

The text of Section 39 answers this. It makes an expert's opinion a relevant fact. It does not make it binding. The court has to "form an opinion" and the expert only helps it do so. In practice this means three things for a student or a young advocate:

• The expert should show qualifications and experience in the specific field, not only a general degree.
• The reasons matter more than the conclusion, which is why Section 45 makes the grounds relevant.
• Expert evidence is usually read along with other evidence. It can confirm an eyewitness or cast doubt on one, but it is weighed like any other evidence.

In criminal trials, Section 329 BNSS adds a practical shortcut. A report from a listed government scientific expert, such as a Chemical Examiner, the Director of a Finger Print Bureau, the Director or Deputy or Assistant Director of a Central or State Forensic Science Laboratory, or the Serologist to the Government, may be used as evidence without calling the expert. The court may still summon and examine the expert, and if the expert cannot attend, a responsible officer conversant with the case may be sent unless the court has directed personal appearance.

What happens when a witness turns hostile?

Ordinarily, the party who calls a witness conducts only the examination-in-chief and cannot ask leading questions. If the witness then goes back on what they told the police, or plainly helps the other side, the party is stuck. Section 157(1) solves this: the court "may, in its discretion" permit the person who calls a witness to put any question which might be put in cross-examination by the adverse party. That is what lawyers mean when they say a witness was "declared hostile".

Section 157(2) then says that nothing in the section disentitles the party so permitted from relying on any part of the evidence of that witness. So the testimony is not thrown out. Suppose a neighbour in Madurai tells the police she saw the accused leave the tenant's house at night, then in court says she saw nothing that night but admits the accused lived next door. The admitted part can still be used, if the court finds it reliable after careful scrutiny.

Once permission is given, the usual tools of cross-examination are open:

1. Previous written statements, Section 148: the witness can be cross-examined on an earlier statement in writing without it being shown to them first, but if it is to be used to contradict them, their attention must be drawn to the specific parts before the writing is proved.
2. Statements to the police, Section 181 BNSS: such a statement cannot otherwise be used at the trial, but the accused may use it to contradict a prosecution witness, and the prosecution may do so only with the court's permission, in the manner provided by Section 148 BSA. The Explanation adds that a significant omission may amount to a contradiction, which is a question of fact.
3. Impeaching credit, Section 158: the adverse party, or the party who called the witness with the court's consent, may show that the witness is unworthy of credit, was bribed or corruptly induced, or made former statements inconsistent with the present evidence.

How should you write about this in an exam?

A ten or fifteen mark answer on either topic reads well when it follows a clear order:

1. Start with the BSA section and give the old Evidence Act number in brackets.
2. Define the term in one or two lines, using the words of the statute ("specially skilled", "in its discretion").
3. Explain the rule with one illustration from the Act and one example of your own.
4. State the weight point: expert opinion is relevant but not conclusive, and hostile testimony is not wiped out under Section 157(2).
5. Link the BNSS provisions (Sections 181 and 329) if the question is about a criminal trial.
6. Cite cases only if you are sure of the name and year. Your teacher's case list and the reported judgment are the safest places to confirm them.

Students who want to see how witnesses are examined in real hearings can ask about court visits through the college legal aid clinic.

Sources

• Bharatiya Sakshya Adhiniyam, 2023 (India Code): official text of the Act, including Sections 39 to 45.
• Bharatiya Sakshya (Second) Bill, 2023 (PRS India): Bill as introduced, showing the arrangement of Chapter X on examination of witnesses.
• BSA Section 39: bare text on opinions of experts and the Examiner of Electronic Evidence.
• BSA Section 41: bare text on opinion as to handwriting and electronic signature.
• BSA Section 148: bare text on cross-examination as to previous statements in writing.
• BSA Section 157: bare text on questions by a party to his own witness.
• BSA Section 158: bare text on impeaching the credit of a witness.
• BNSS Section 181: bare text on statements to police and their use.
• BNSS Section 329: bare text on reports of certain government scientific experts.