Section 173(8) permits further investigation by the investigation officer. Even without the order of Magistrate investigating officer is free to conduct further investigation. It must be noted here that Code does not mandate taking prior permission from the Magistrate if the police wants to conduct further investigation suo motu.
Supreme Court in Ram Lal Narang v. State (Delhi Administration), (1979) 2 SCC 322 was posed with the question whether it is necessary for the police to take formal permission from the Magistrate for further investigation? However, Supreme Court held that as a matter of proprietary, interest of administration of justice and independence of magistracy and not as a matter of law, it is prudent for the investigating officer to take a formal permission from the Magistrate. In later case, in Rama Chaudhary v. State of Bihar, (2009) 6 SCC 346 Supreme Court has clearly mentioned that law does not mandate taking prior permission from the Magistrate for conducting further investigation. It is a statutory right of the police. Such investigation can be conducted even if police report is submitted under Section 173(2). Therefore, the position of law which flows from these two judgment is that although Section 173(8) does not require the permission of Magistrate to conduct further investigation but still as a matter of prudence police should take a formal permission from the Magistrate. If the police fails to take such formal permission absolutely no affect will be had on the investigation.
Further investigation is continuation of previous investigation. If after submission of police report investigating officer is of the opinion that further evidence is to be collected then he can continue with further investigation. Whatever evidence is collected in further investigation becomes the part of police report by filing supplementary police report. Supreme Court in Ramchandran v. R. Udhayakumar and Ors., AIR 2008 SC 3102 held that in further investigation the previous investigation is not wiped out. Supreme Court in Hasanbhai Valibhai Qureshi v. State of Gujarat and Ors. (2004) 5 SCC 347 held that prime consideration for further investigation is to arrive at the truth and do real and substantial justice.
Neither the prosecution nor the informant can claim as a matter of right a direction for further investigation. Section 173(8) provides that even after the submission of police report under Section 173(2) the investigating agency can conduct the further investigation and if any additional evidence is found then the same can be send in form of supplementary report.
It must be noted here that in Section 173(8) the power of Magistrate to order further investigation has not been mentioned but the Supreme Court in State of Bihar v. JAC Saldhana, (1980) 1 SCC 554 held that the further investigation can be ordered by Magistrate under Section 156(3) even after police report has been submitted. Similar view was echoed by Supreme Court in Amrutbhai Shambhubhai Patel v. Sumanbhai Kantibhai Patel, (2017) 4 SCC 177. The power of Magistrate under Section 156(3) to direct further investigation is an independent power and does not stand in conflict with the power of police to conduct further investigation under Section 173(8).
Thus, further investigation can be conducted by investigating officer per se i.e. without the order of Magistrate and on the other hand Magistrate is also empowered to order further investigation under Section 156(3) read with Section 173(8).
Further investigation after taking cognizance: Supreme Court in Vinubhai Haribhai Malviya and Others v. State of Gujarat, 2019 (3) ALT Cri 284 (SC) held that the Magistrate has power under Section 156(3) to order further investigation even at post cognizance stage until trial commences. This power can also be exercised suo motu by Magistrate. Whether further investigation should be ordered or should not be ordered is the discretion of the Magistrate depending upon facts of each case.
Re-investigation: There is no concept of re-investigation in Code. Re-investigation means de novo investigation or fresh investigation wiping out the previous investigation. Supreme Court in Vinay Tyagi v. Irshad Ali, (2013) 5 SCC 762has made explicitly clear that Magistrate cannot order re-investigation and police also cannot conduct re-investigation on its own. Re-investigation can only be ordered in exceptional circumstances by superior courts like High Courts or Supreme Court under their inherent powers. These superior courts can order re-investigation only where the investigation is ex facie tainted, unfair or mala fide. In Vinay Tyagi’s case Supreme Court made it clear that when re-investigation is ordered and there is no specific direction about the status of previous investigation, such previous investigation will form part of record. If the courts want that such previous investigation do not form part of record there must be specific direction to that effect.