A) ABSTRACT / HEADNOTE

The Constitution Bench judgment in Mukesh Singh v. State (Narcotic Branch of Delhi) resolves a long-standing judicial conflict on whether a criminal trial under the Narcotic Drugs and Psychotropic Substances Act, 1985 stands vitiated when the informant/complainant police officer himself conducts the investigation. The reference arose due to divergent judicial opinions, culminating in the decision of Mohan Lal v. State of Punjab (2018), which had held that such a course automatically vitiates the trial. The present five-Judge Bench undertook an exhaustive examination of the statutory scheme of the Code of Criminal Procedure, 1973, the NDPS Act, constitutional guarantees under Article 21, and the doctrine of fair investigation.

The Court held that there is no statutory or constitutional bar preventing the informant from acting as the investigating officer. Sections 154, 156, and 157 CrPC positively mandate that the officer receiving information of a cognizable offence must record and investigate it. The NDPS Act, though a special statute with stringent provisions and reverse burden clauses under Sections 35 and 54, does not prohibit such investigation. The Court emphasized that prejudice and bias cannot be presumed and must be specifically pleaded and proved. The judgment expressly overruled Mohan Lal and similar precedents to the extent they laid down a blanket rule of invalidity. The ruling restores a fact-centric approach, reinforcing that fairness of investigation is to be assessed during trial, not presumed at inception.

Keywords: NDPS Act, Informant-Investigator, Fair Investigation, Article 21, Reverse Burden of Proof

B) CASE DETAILS

C) INTRODUCTION AND BACKGROUND OF JUDGMENT

The reference before the Constitution Bench stemmed from conflicting judicial opinions on the permissibility of an informant police officer conducting the investigation in NDPS prosecutions. Earlier decisions such as Bhagwan Singh, Megha Singh, and Rajangam had expressed reservations rooted in apprehensions of bias. This line culminated in Mohan Lal v. State of Punjab (2018), which elevated the principle into a rigid rule, holding that such investigations ipso facto violate Article 21 and vitiate the trial.

Subsequently, in Varinder Kumar v. State of Himachal Pradesh, a three-Judge Bench confined Mohan Lal to prospective operation, casting doubt on its doctrinal soundness. The present reference required authoritative clarification. The Court undertook a granular statutory analysis of the CrPC scheme governing cognizable offences and juxtaposed it with the procedural architecture of the NDPS Act.

The Bench examined whether constitutional notions of fair investigation require a complete institutional separation between informant and investigator. Emphasis was placed on legislative intent, safeguards embedded in the NDPS Act, and settled principles that irregularities in investigation do not automatically nullify trials absent demonstrable prejudice. The background thus reflects a tension between abstract fairness doctrines and practical statutory mandates.

D) FACTS OF THE CASE

The appeals arose from NDPS prosecutions where the officer who received secret information, effected seizure, and lodged the complaint also proceeded to investigate the offence. The accused challenged the validity of such investigations relying on Mohan Lal, contending that the dual role created an inherent bias.

The High Court of Delhi had upheld the conviction, rejecting the argument that the investigation stood vitiated solely on this ground. In view of conflicting Supreme Court precedents, the matter was escalated. The central factual premise across connected matters was identical: no allegation of actual bias or fabrication was established, and the challenge rested purely on the legal permissibility of the informant-investigator role.

The prosecution relied on statutory compliance under Sections 42, 50, 52, and 57 NDPS Act and emphasized that safeguards were duly followed. Independent witnesses were either unavailable or hostile, a recurring feature in narcotics prosecutions. These facts framed the narrow but significant legal question requiring authoritative resolution.

E) LEGAL ISSUES RAISED

i. Whether an investigation under the NDPS Act is vitiated when the informant police officer himself conducts the investigation?
ii. Whether such investigation violates the guarantee of a fair trial under Article 21?
iii. Whether the reverse burden under Sections 35 and 54 NDPS Act mandates a stricter rule of separation?

F) PETITIONER / APPELLANT’S ARGUMENTS

The counsels for the appellants submitted that allowing the complainant to investigate offends the nemo judex in causa sua principle. It was argued that NDPS offences hinge critically on possession and recovery, making neutrality of investigation indispensable. Heavy reliance was placed on Mohan Lal, asserting that reverse burden provisions intensify the risk of false implication. The appellants contended that Sections 42 and 53 NDPS Act envisage distinct roles and that permitting overlap defeats statutory safeguards and constitutional fairness.

G) RESPONDENT’S ARGUMENTS

The counsels for the State argued that Sections 154, 156, and 157 CrPC impose a duty on the officer receiving information to investigate. The NDPS Act does not bar such investigation and expressly applies CrPC procedures through Section 51. It was contended that bias cannot be presumed, and fairness must be assessed on evidence during trial. The State emphasized Section 58 NDPS Act as an inbuilt safeguard against malicious action.

H) JUDGMENT 

The Constitution Bench categorically held that there is no legal prohibition against the informant acting as the investigator. The Court clarified that CrPC provisions mandate continuity between receipt of information and investigation. The NDPS Act, though stringent, does not override this framework.

The Court rejected the assumption-based approach in Mohan Lal, holding that prejudice must be proved, not presumed. It relied on Section 465 CrPC and Illustration (e) to Section 114 Evidence Act, underscoring that official acts carry a presumption of regularity. The Bench further noted that reverse burden provisions do not alter investigation norms and that prosecution must still discharge its initial burden.

The Court overruled Mohan Lal and all decisions laying down a contrary general proposition.

a) RATIO DECIDENDI

The ratio rests on statutory interpretation and constitutional balance. The Court held that fair investigation under Article 21 is contextual, not abstract. Absence of statutory bar, coupled with procedural safeguards and judicial scrutiny during trial, negates any automatic vitiation. Bias must be established through evidence.

b) OBITER DICTA

The Court observed that in cases where investigation is solely dependent on the testimony of the informant-investigator and demonstrable prejudice is shown, courts may accord appropriate weight while appreciating evidence.

c) GUIDELINES

i. Informant-investigator investigations are legally permissible.
ii. No automatic acquittal arises from such investigation.
iii. Courts must assess actual prejudice during trial.
iv. Mohan Lal stands overruled.

I) CONCLUSION & COMMENTS

The judgment restores doctrinal coherence by aligning constitutional fairness with statutory mandates. It rejects formalistic presumptions and reinforces evidence-based adjudication. The ruling has far-reaching implications for NDPS prosecutions and criminal procedure jurisprudence, reaffirming that fairness is a matter of proof, not presumption.

J) REFERENCES

a) Important Cases Referred

1. Mohan Lal v. State of Punjab (2018) 17 SCC 627
2. Varinder Kumar v. State of Himachal Pradesh (2020) 3 SCC 321
3. Bhagwan Singh v. State of Rajasthan (1976) 1 SCC 15

b) Important Statutes Referred

1. Code of Criminal Procedure, 1973
2. Narcotic Drugs and Psychotropic Substances Act, 1985
3. Constitution of India