Section 44 of Evidence Act "Fraud or collusion in obtaining judgment, or incompetency of Court, may be proved"
Any party to a suit or other proceeding may show that any judgment, order or decree which is relevant under section 40, 41 or 42 and which has been proved by the adverse party, was delivered by a Court not competent to deliver it, or was obtained by fraud or collusion.
When the Court has to form and opinion upon a point of foreign law or of science or art, or as to identity of handwriting [ or finger impressions], the opinions upon that point of persons specially skilled in such foreign law, science or art, [ or in questions as to identity of handwriting ] [ or finger impressions ] are relevant facts.
Such persons are called experts.
Illustrations
(a) The question is, whether the death of A was caused by
poison.
The opinions of experts as to the symptoms produced by the
poison by which A is supposed to have died, are relevant.
(b) The question 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.