Can an Illegal Arrest Make the Entire Investigation Legally Vulnerable?

Can an Illegal Arrest Make the Entire Investigation Legally Vulnerable?

Introduction

Arrest is one of the most serious interventions by the State into an individual’s personal liberty. Although criminal investigation is essential for maintaining law and order, the power to arrest is subject to constitutional and statutory safeguards.
The Bharatiya Nagarik Suraksha Sanhita, 2023 (BNSS) has replaced the Code of Criminal Procedure, 1973 and continues the legal framework governing arrest, detention, investigation and remand. Alongside these statutory provisions, Articles 21 and 22 of the Constitution of India provide fundamental safeguards to an arrested person.
An important question has therefore emerged in recent criminal jurisprudence: if an arrest is illegal because mandatory safeguards were not followed, does that illegality affect everything that happens during the investigation?
The answer requires a distinction. An illegal arrest can have serious consequences for the legality of custody and remand, but it does not automatically mean that every subsequent investigative step or the entire criminal case becomes void. The consequences depend upon the nature of the violation and the applicable legal remedy.

Constitutional Safeguards Against Arbitrary Arrest

Article 21 provides that no person shall be deprived of life or personal liberty except according to procedure established by law.
Article 22(1) provides an additional safeguard by requiring that an arrested person be informed, as soon as may be, of the grounds of arrest and be allowed to consult and be defended by a legal practitioner of their choice.
These protections are not merely technical requirements. They enable an arrested person to understand why liberty has been curtailed and to effectively challenge the arrest, oppose police custody and seek bail.

The Supreme Court has repeatedly treated the communication of grounds of arrest as a substantive constitutional safeguard.
What Does the BNSS Provide?

Under Section 35 BNSS, the statute regulates circumstances in which a police officer may arrest without warrant and prescribes safeguards surrounding the exercise of that power.
Section 47 BNSS specifically provides that a person arrested without warrant must be informed of the grounds of arrest and, where applicable, of the right to bail.
Section 48 BNSS concerns the obligation to inform a relative, friend or other person nominated by the arrested person about the arrest.
These provisions operate alongside Article 22. Therefore, the legality of an arrest must be examined not only by asking whether the police had statutory power to arrest but also whether the constitutional and procedural safeguards were actually complied with.

Supreme Court: Vihaan Kumar v. State of Haryana
A significant decision is Vihaan Kumar v. State of Haryana, 2025 INSC 162, decided by the Supreme Court on 7 February 2025.
The appellant challenged his arrest on the ground that he had not been informed of the grounds of arrest as required under Article 22(1). The Supreme Court held that informing an arrested person of the grounds of arrest is a mandatory constitutional requirement.
The Court further clarified an important distinction: information about the fact of arrest is not the same thing as communication of the grounds of arrest. An arrest memo containing basic details such as the FIR number, offences invoked, date and time of arrest does not, by itself, necessarily communicate the grounds on which the particular person has been arrested.
On the facts before it, the Supreme Court held that the arrest was vitiated because the grounds of arrest had not been communicated. However, the Court expressly clarified that this finding did not affect the merits of the charge-sheet or the pending criminal case.
This distinction is particularly important: an illegal arrest and an invalid prosecution are not necessarily the same thing.

Mihir Rajesh Shah: A Major Development
The jurisprudence developed further in Mihir Rajesh Shah v. State of Maharashtra, (2026) 1 SCC 500.
The Supreme Court considered the constitutional requirement of communicating the grounds of arrest and its relationship with Section 47 of the BNSS.
The Court held that the grounds of arrest must be communicated in writing to the arrested person. Where immediate written communication is impracticable, the grounds may initially be communicated orally, but written grounds must subsequently be supplied within a reasonable time and, in any event, at least two hours before production before the Magistrate for remand proceedings. The Court further held that non-compliance can render the arrest and subsequent remand illegal.
The decision is significant because it connects the statutory requirement under Section 47 BNSS with the fundamental rights guaranteed under Articles 21 and 22.
It also emphasises the practical purpose of communicating the grounds: the arrested person must have sufficient information to consult counsel, challenge the arrest, oppose police custody and seek bail.

Prabir Purkayastha and the Effect of Subsequent Events
The Supreme Court’s earlier decision in Prabir Purkayastha v. State (NCT of Delhi), (2024) 8 SCC 254 is another important authority.
The Court treated communication of the grounds of arrest as a constitutional safeguard and held that failure to comply with the requirement could vitiate the arrest and subsequent police custody remand. Importantly, the Court rejected the argument that subsequent events, such as filing of a charge-sheet, could automatically cure an unconstitutional arrest and initial police remand.
The principle is therefore that a later procedural event cannot retrospectively convert an unconstitutional deprivation of liberty into a lawful one.

Does an Illegal Arrest Invalidate the Entire Investigation?

This is where careful legal analysis becomes necessary.
An illegal arrest does not automatically invalidate the entire investigation.
The Supreme Court demonstrated this distinction in Vihaan Kumar. Although the arrest was held to be vitiated, the Court specifically stated that the finding did not affect the merits of the charge-sheet or the pending criminal case.

Therefore, three questions should be kept separate:

First — Was the arrest lawful? The Court examines whether the statutory conditions for arrest and constitutional safeguards were satisfied.

Second — Was the detention or remand lawful? Even if the investigation itself continues, an unlawful arrest may have consequences for police custody or subsequent remand.

Third — Were later investigative acts independently lawful? Searches, seizures, statements, recoveries, electronic evidence and other investigative steps must be examined according to the legal provisions applicable to each act.
Consequently, the phrase “illegal arrest makes the entire investigation illegal” should not be treated as an absolute rule.

Recent Judicial Developments
The significance of these safeguards has continued into 2026.
In Dr. Rajinder Rajan v. Union of India, decided on 1 April 2026, the Supreme Court considered the failure to furnish written grounds of arrest in the context of an NDPS prosecution and applied the principles concerning Articles 21 and 22 and Mihir Rajesh Shah.

The Gauhati High Court’s decision in Mujammel Hoque v. State of Assam, dated 3 September 2026, also examined the constitutional significance of informing a person of the grounds of arrest. The judgment discussed Prabir Purkayastha, Vihaan Kumar and Mihir Rajesh Shah, reiterating that Article 22 protection is connected with the individual’s ability to challenge detention and secure legal assistance.

These developments demonstrate the continuing judicial focus on arrest safeguards under the post-BNSS criminal procedure framework.

Why These Safeguards Matter
The requirement to communicate grounds of arrest serves several purposes.
It allows the accused to understand the allegations forming the basis of the arrest. It enables meaningful consultation with a lawyer. It allows the accused to challenge the legality of custody and oppose police remand. It also provides courts with a mechanism to scrutinise whether the State has complied with constitutional requirements.
For investigating agencies, proper documentation of compliance is equally important. An arrest that is substantively justified may nevertheless become legally vulnerable if mandatory procedural safeguards are ignored.

Conclusion
The law therefore draws an important line between an illegal arrest and an invalid investigation.
Failure to communicate the grounds of arrest can have serious constitutional consequences. Under Article 22(1), Section 47 BNSS and the Supreme Court’s recent jurisprudence, such compliance is not merely a formality. Depending on the circumstances, non-compliance may render the arrest and subsequent remand illegal.
At the same time, an illegal arrest does not automatically erase the investigation, charge-sheet or every item of evidence collected thereafter. Each subsequent investigative act must be examined independently under the applicable law.
The emerging principle is therefore clear: criminal investigation must remain within the boundaries of constitutional liberty and statutory procedure.
For both investigating agencies and defence counsel, the legality of the arrest, the communication of grounds, the validity of remand and the legality of subsequent investigative steps must be carefully examined as distinct but interconnected questions.

Lexel Law – Legal Services & Litigation Chambers | Chandigarh