This question has been definitively dealt with by a Constitution Bench of this Court in Masalti v. State of Uttar Pradesh, AIR 1965 SC 202, wherein the Court observed as under:
… under the Indian Evidence Act, trustworthy evidence given by a single witness would be enough to convict an accused person, whereas evidence given by half a dozen witnesses which is not trustworthy would not be enough to sustain the conviction. That, no doubt is true; but where a criminal court has to deal with evidence pertaining to the commission of an offence involving a large number of offenders and a large number of victims, it is usual to adopt the test that the conviction could be sustained only if it is supported by two or three or more witnesses who give a consistent account of the incident. In a sense, the test may be described as mechanical; but it is difficult to see how it can be treated as irrational or unreasonable.
In Muthu Naicker and Ors. v. State of Tamil Nadu, AIR 1978 SC 1647, this Court explained the aforesaid judgment by stating that in a situation where a witness has been attacked by the members of an unlawful assembly composed of a large number of persons, the court should carefully consider the question of the credibility of such a witness. Where the court is of the view that the testimony of such a witness is in the facts and circumstances of the case not reliable, it should insist that such testimony be corroborated by one or more other witness before it can be accepted by the court.
A similar view has also been taken by this Court in Binay Kumar Singh v. State of Bihar, AIR 1997 SC 322, wherein the Court has held:
There is no rule of evidence that no conviction can be based unless a certain minimum number of witnesses have identified a particular accused as a member of the unlawful assembly. It is axiomatic that evidence is not to be counted but only weighed and it is not the quantity of evidence but the quality that matters. Even the testimony of one single witness, if wholly reliable, is sufficient to establish the identification of an accused as a member of an unlawful assembly. All the same, when the size of the unlawful assembly is quite large (as in this case) and many persons would have witnessed the incident, it would be a prudent exercise to insist on at least two reliable witnesses to vouchsafe the identification of an accused as a participant in the rioting.
Similarly, in Kamaksha Rai and Ors. v. State of Uttar Pradesh, (1999) 8 SCC 701, this Court observed:
Taking into consideration the nature of attack and the possibility or otherwise of the identification of these accused persons by the prosecution witnesses and bearing in mind the principles laid down by this Court in the above- cited judgments, we are of the opinion that it is not safe to rely on the evidence of witnesses who speak generally and in an omnibus way without specific reference to the identity of the individuals and their specific overt acts in regard to the incident ….
Consequently, the Court took the view that in the facts and circumstances of the case, as a lot of witnesses had referred to the accused in a vague and general manner rather than making specific reference to the identity of the individuals and their specific overt acts in the incident, prudence dictated that it was necessary to fix a minimum number of witnesses needed to accept the prosecution case to base a conviction.
A similar view has been reiterated by this Court in Chandra Shekhar Bind and Ors. v. State of Bihar, (2001) 8 SCC 690.