Step 1: Recall what is being asked - the statutory home of the insanity defence in Indian law. The M'naghten rule supplies the criterion: a mentally unsound accused who cannot appreciate the nature of his act, or that it is wrong or unlawful, escapes criminal liability.
Step 2: Indian criminal law codifies this exact idea under Section 84 of the IPC. The key phrase $unsoundness\ of\ mind$ in that section directly mirrors the M'naghten wording, anchoring the rule to IPC 84.
Step 3: Eliminate the distractors. The Criminal Procedure Code (CrPC) and the Civil Procedure Code (CPC) govern procedure, not substantive insanity, ruling out CrPC 84 and CPC 48. IPC 48 concerns the meaning of a vessel, which is unrelated.
Step 4: The only section matching the substantive insanity defence is therefore IPC 84.
\[\boxed{IPC\ 84}\]