Sec. 45 to Sec.51 under Chapter-II of the Indian Evidence Act provide relevancy of opinion of third persons, which is commonly called in our day to day practice as expert’s opinion. These provisions are exceptional in nature to the general rule that evidence is to be given of the facts only which are within the knowledge of a witness. The exception is based on the principle that the court can’t form opinion on the matters, which are technically complicated and professionally sophisticated, without assistance of the persons who have acquired special knowledge and skill on those matters. Conditions for admitting an expert opinion are following:-
a)      That the dispute can’t be resolved without expert opinion and
b)Â Â Â Â Â Â That the witness expressing the opinion is really an expert.
Who is an expert?
The definition of an expert may be referred from the provision of Sec.45 of Indian Evidence Act that an ‘Expert’ means a person who has special knowledge, skill or experience in any of the following—-
1)Â Â Â Â Â Â foreign law,
2)Â Â Â Â Â Â science
3)Â Â Â Â Â Â art
4)Â Â Â Â Â Â handwriting or
5)Â Â Â Â Â Â finger impression
and such knowledge has been gathered by him—
a)Â Â Â Â Â Â by practice,
b)Â Â Â Â Â Â observation or
c)Â Â Â Â Â Â proper studies.
For example, medical officer, chemical analyst, explosive expert, ballistic expert, fingerprint expert etc.
According to Sec.45, the definition of an expert is confined only to the five subjects or fields as mentioned above. But practically there are some more subjects or fields on which court may seek opinion an expert.
An expert witness is one who has devoted time and study to a special branch of learning and thus he is specially skilled on those points on which he is asked to state his opinion. His evidence on such points is admissible to enable the court to come to a satisfactory conclusion.
Duty of the expert:-
a)Â An expert is not a witness of fact.
b)His evidence is of advisory character.
c)Â An expert deposes and does not decide.
d)Â An expert witness is to furnish the judge necessary scientific criteria for testing the accuracy of the conclusion so as to enable the judge to form his independent judgment by application of the criteria to the facts proved by the evidence.
Value of expert opinion:-
The Expert evidence has two aspects —
a) Data evidence  [it can’t be rejected if it is inconsistent to oral evidence]
b) Opinion evidence  [it is only an inference drawn from the data and it would not get precedence over the direct eye-witness testimony unless the inconsistency between the two is so great as to falsify the oral evidence] –[Arshad v. State of A.P. 1996 CrLJ 2893 (para34) (AP)]
