There is no provision in Criminal Procedure Code which speaks about amendment of a First Information Report registered under Section 154 CrPC.
The question whether an FIR can be ‘amended’ is seen considered by Madras High Court in R.Westly vs Union Of India (2019).
While holding that an FIR once registered cannot be amended, Justice P N Prakash noted that there is a practice of filing an alteration memo by investigation authorities. The judge said: That there is no provision in the Code of Criminal Procedure for filing an alteration memo is indeed true. But, filing an alteration memo is a procedure that is adopted by the Investigating Agencies from time immemorial in the State of Tamil Nadu which is fossilized into an accepted practice. Any procedure or practice which has been in vogue for a long time and which does not violate any law, need not be jettisoned on the ground that there is no statutory backing for it….For example, when a person is attacked brutally and is alive, the police will register an FIR under Section 307 IPC and send the FIR to the Court. If, after a few days, the injured dies, the case will be altered to one under Section 302 IPC and the alteration report will be sent to the Court to inform the Court about the alteration made in the case. Filing of an alteration memo by the police is not for amending the FIRs, because, an FIR once registered cannot be amended. Filing an alteration memo is an intimation to the Court that the Investigating Officer is now investigating a case of murder and not attempt to murder.
The court said that filing of this alteration memo is merely an intimation to the trial Court about the route that is being taken by the Investigating Agency in the investigation of the case. It does not require the formal nod of any Court, because, investigation completely falls within the domain of the Investigating Agency, of course, to be generally monitored by the Magistrate (in this case, the Special Court) and nothing beyond that, it said.
But in T.T. Antony v. State of Kerala (2001)6 SCC 181, the Supreme Court had made this observation:
Take a case where an FIR mentions cognizable offence under Section 307 or 326 IPC and the investigating agency learns during the investigation or receives fresh information that the victim died, no fresh FIR under Section 302 IPC need be registered which will be irregular; in such a case alteration of the provision of law in the first FIR is the proper course to adopt. Let us consider a different situation in which H having killed W, his wife, informs the police that she is killed by an unknown person or knowing that W is killed by his mother or sister, H owns up the responsibility and during investigation the truth is detected; it does not require filing of fresh FIR against H — the real offender — who can be arraigned in the report under Section 173(2) or 173(8) CrPC, as the case may be. It is of course permissible for the investigating officer to send up a report to the Magistrate concerned even earlier that investigation is being directed against the person suspected to be the accused.