Quality Determines the Adequacy of Evidence

“19. In the matter of appreciation of evidence of witnesses, it is not the number of witnesses but quality of their evidence which is important, as there is no requirement under the Law of Evidence that any particular number of witnesses is to be examined to prove/disprove a fact. It is a time-honoured principle that evidence must be weighed and not counted. The test is whether the evidence has a ring of truth, is cogent, credible and trustworthy or otherwise. The legal system has laid emphasis on value provided by each witness, rather than the multiplicity or plurality of witnesses. It is quality and not quantity, which determines the adequacy of evidence as has been provided by Section 134 of the Evidence Act. Even in probate cases, where the law requires the examination of at least one attesting witness, it has been held that production of more witnesses does not carry any weight. Thus, conviction can even be based on the testimony of a sole eyewitness, if the same inspires confidence.
(Vide Vadivelu Thevar v. State of Madras [AIR 1957 SC 614: 1957 Cri LJ 1000] , Kunju v. State of T.N. [(2008) 2 SCC 151: (2008) 1 SCC (Cri) 331] , Bipin Kumar Mondal v. State of W.B. [(2010) 12 SCC 91: (2011) 2 SCC (Cri) 150 : AIR 2010 SC 3638] , Mahesh v. State of M.P. [(2011) 9 SCC 626 : (2011) 3 SCC (Cri) 783], Prithipal Singh v. State of Punjab [(2012) 1 SCC 10 : (2012) 1 SCC (Cri) 1] and Kishan Chand v. State of Haryana [(2013) 2 SCC 502 : (2013) 2 SCC (Cri) 807: JT (2013) 1 SC 222].)”

Supreme Court
Gulam Sarbar v. State of Bihar, (2014) 3 SCC 401