How far Evidence of Police Witnesses is Reliable, Credible

In Baldev Singh v. State of Haryana reported in (2015) 17 SCC 554, it has been held:

There is no legal proposition that evidence of police officials unless supported by independent evidence is unworthy of acceptance. Evidence of police witnesses cannot be discarded merely on the ground that they belong to police force and interested in the investigation and their desire to see the success of the case. Prudence however requires that the evidence of police officials who are interested in the outcome of the result of the case needs to be carefully scrutinized and independently appreciated. Mere fact that they are police officials does not by itself give rise to any doubt about their creditworthiness.

Observing that no infirmity is attached to the testimony of police officials merely because they belong to police force and that conviction can be based on the testimony of police officials in Girja Prasad v. State of M.P., (2007) 7 SCC 625, it was held as under:-

It is well-settled that credibility of witness has to be tested on the touchstone of truthfulness and trustworthiness. It is quite possible that in a given case, a Court of Law may not base conviction solely on the evidence of Complainant or a Police Official but it is not the law that police witnesses should not be relied upon and their evidence cannot be accepted unless it is corroborated in material particulars by other independent evidence. The presumption that every person acts honestly applies as much in favour of a Police Official as any other person. No infirmity attaches to the testimony of Police Officials merely because they belong to Police Force. There is no rule of law which lays down that no conviction can be recorded on the testimony of Police Officials even if such evidence is otherwise reliable and trustworthy. The rule of prudence may require more careful scrutiny of their evidence. But, if the Court is convinced that what was stated by a witness has a ring of truth, conviction can be based on such evidence.

Before more than half-a-century, in the leading case of Aher Raja Khima v. State of Saurashtra, AIR 1956 SC 217, Venkatarama Ayyar, J. stated:

The presumption that a person acts honestly applies as much in favour of a police officer as of other persons, and it is not judicial approach to distrust and suspect him without good grounds therefor. Such an attitude could do neither credit to the magistracy nor good to the public. It can only run down the prestige of the police administration.

In Tahir v. State (Delhi), (1996) 3 SCC 338, dealing with a similar question, Dr. A.S. Anand, J. (as His Lordship then was) stated: 

Where the evidence of the police officials, after careful scrutiny, inspires confidence and is found to be trustworthy and reliable, it can form basis of conviction and the absence of some independent witness of the locality to lend corroboration to their evidence, does not in any way affect the creditworthiness of the prosecution case.