²[45.  When the Court has to form an opinion upon a point of foreign law, or of science, physical or forensic evidence or digital record, or art, or as to identity of hand writing or finger impression or footprint or palm impression or iris impression or typewriting or usage of trade or technical terms or identity of person or animal, the opinion upon that point of person specially skilled in such foreign law, science, physical or forensic evidence or digital record or art, or in questions as to identity of handwriting or finger impression, footprint, palm impression, typewriting, usage of trade, technical term or identity of person or animal, as the case may be, are relevant facts.

Such persons are called experts.

Illustrations

(a) The question is, whether the death of A was caused by poison.

The opinion of experts as to the symptoms produced by the poison by which A is supposed to have died, are relevant.

(b) The questions is, whether A, at the time of doing a certain act, was, by reason of unsoundness of mind, incapable of knowing the nature of the act, or that he was doing what was either wrong or contrary to law.

The opinions of experts upon the question whether the symptoms exhibited by A commonly show unsoundness of mind, and whether such unsoundness of mind usually renders persons incapable of knowing the nature of the acts which they do, or of knowing that what they do is either wrong or contrary to law, are relevant.

(c) The question is whether a certain document was written by A. Another document is produced which is proved or admitted to have been written by A.

The opinions of experts on the question whether the two documents were written by the same person or by different persons, are relevant.]

³[45A. (1) Except by leave of the Court a witness shall not testify as an expert on physical or forensic unless a copy of his report has, pursuant to sub-section (2), been given to all the parties.

(2) An expert’s report shall be addressed to the Court and not to the party on whose behalf he is examined and he shall owe a duty to help the Court.]

46. Facts, not otherwise relevant, are relevant if they support or are inconsistent with the opinions of experts, when such opinions are relevant.

Illustrations

(a) The question is, whether A was poisoned by a certain poison.

The fact that other persons, who were poisoned by that poison, exhibited certain symptoms which experts affirm or deny to be the symptoms of that poison, is relevant.

(b) The question is, whether an obstruction to a harbour is caused by a certain sea-wall.

The fact that other harbours similarly situated in other respects, but where there were no such sea-walls, began to be obstructed at about the same time, is relevant.

47. When the Court has to form an opinion as to the person by whom any document was written or signed, the opinion of any person acquainted with the handwriting of the person by whom it is supposed to be written or signed that it was or was not written or signed by that person, is a relevant fact.

Explanation.–A person is said to be acquainted with the handwriting of another person when he has seen that person write, or when he has received documents purporting to be written by that person in answer to documents written by himself or under his authority and addressed to that person, or when, in the ordinary course of business, documents purporting to be written by that person have been habitually submitted to him.

Illustration

The question is, whether a given letter is in the handwriting of A, a merchant in London.

B is a merchant in Chittagong, who has written letters addressed to A and received letters purporting to be written by him. C is B's clerk, whose duty it was to examine and file B's correspondence. D is B's broker, to whom B habitually submitted the letters purporting to be written by A for the purpose of advising with him thereon.

The opinions of B, C and D on the question whether the letter is in the handwriting of A are relevant, though neither B, C or D ever saw A write.

⁴[47A.  When the Court has to form an opinion as to the digital signature of any person, the opinion of the Certifying Authority which has issued the Digital Signature Certificate is a relevant fact.]

48. When the Court has to form an opinion as to the existence of any general custom or right, the opinions, as to the existence of such custom or right, of persons who would be likely to know of its existence if it existed, are relevant.

Explanation.–The expression "general custom or right" includes customs or rights common to any considerable class of persons.

Illustration

The right of the villagers of a particular village to use the water of a particular well is a general right within the meaning of this section.

50. When the Court has to form an opinion as to the relationship of one person to another the opinion, expressed by conduct, as to the existence of such relationship, of any person who, as a member of the family or otherwise, has special means of knowledge on the subject, is a relevant fact:

Provided that such opinion shall not be sufficient to prove a marriage in proceedings under the Divorce Act, or in prosecutions under section 494, 495, 497 or 498 of the ⁵[* * *] Penal Code.

Illustrations

(a) The question is, whether A and B were married.

The fact that they were usually received and treated by their friends as husband and wife, is relevant.

(b) The question is, whether A was the legitimate son of B. The fact that A was always treated as such by members of the family, is relevant.

51. 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.