157. Procedure for investigation.

(1) If, from information received or otherwise, an officer in charge of a police station has reason to suspect the commission of an offence which he is empowered under section 156 to investigate, he shall forthwith send a report of the same to a Magistrate empowered to take cognizance of such offence upon a police report and shall proceed in person, or shall depute one of his subordinate officers not being below such rank as the State Government may, by general or special order, prescribe in this behalf, to proceed, to the spot, to investigate the facts and circumstances of the case, and, if necessary, to take measures for the discovery and arrest of the offender:
Provided that-
(a) when information as to the commission of any such offence is given against any person by name and the case is not of a serious nature, the officer in charge of a police station need not proceed in person or depute a subordinate officer to make an investigation on the spot;
(b) if it appears to the officer in charge of a police station that there is no sufficient ground for entering on an investigation, he shall not investigate the case.
Provided further that in relation to an offence of rape, the recording of statement of the victim shall be conducted at the residence of the victim or in the place of her choice and as far as practicable by a woman police officer in the presence of her parents or guardian or near relatives or social worker of the locality.

(2) In each of the cases mentioned in clauses (a) and (b) of the proviso to sub-section (1), the officer in charge of the police station shall state in his report his reasons for not fully complying with the requirements to that sub-section, and, in the case mentioned in clause (b) of the said proviso, the officer shall also forthwith notify to the informant, if any, in such manner as may be prescribed by the State Government, the fact that he will not investigate the case or cause it to be investigated.

Comments:
Section 157 casts a duty upon the investigating officer to forthwith send the report of the cognizable offence to the concerned Magistrate The purpose for forthwith sending the report to the concerned Magistrate is to keep the concerned Magistrate informed of the investigation of a cognizable offence so that he may be able to control the investigation and if required, to issue appropriate directions Mere delay in the despatch of the FIR itself is no ground to throw away the prosecution case in its entirety Sending the report to the concerned Magistrate is a circumstance which provides a basis to raise suspicion that the FIR is the result of consultation and deliberations and it was recorded much later than the date and time mentioned in it, and discloses that the investigation is not fair and forth right;
Swati Ram v State of Rajasthan, (1997)