“In the case of Mohan Lal this Court observed, in a case where the informant and the investigator is the same, the trial is vitiated and the accused is entitled to acquittal. Varinder Kumar held, the decision in the case of Mohan Lal shall be applicable prospectively and shall not affect the cases, pending criminal prosecutions, trials and appeals and they shall be governed by the individual facts of the case.
The NDPS Act does not specifically bar the informant/complainant to be an investigator. Therefore, as such, there is no reason to doubt the credibility of the informant and doubt the entire case of the prosecution solely on the ground that the informant has investigated the case. Solely on the basis of some apprehension or doubts, the entire prosecution version cannot be discarded and the accused is not to be straightway acquitted unless and until the accused is able to establish and prove the bias and the prejudice. The question of prejudice or bias has to be established and not inferred.
Therefore, merely because the informant is the investigator, by that itself the investigation would not suffer the vice of unfairness or bias and… the accused is not entitled to acquittal. The matter has to be decided on a case to case basis. A contrary decision of this Court in the case of Mohan Lal v. State of Punjab, (2018) 17 SCC 627 and any other decision taking a contrary view are not good law and they are specifically overruled.”
– Hon’ble Justice M.R. Shah, Mukesh Singh v. State, [SLP (Criminal) Diary No. 39528 of 2018].