If the police fail to do their job in a cognizable offence, the magistrate has the authority to order an investigation. A magistrate may either instruct the police officer to investigate the matter or substitute a magisterial inquiry conducted by himself or his deputies.
However, the question is whether a magistrate has also the power to stop an investigation by police or not.
To further comprehend this, two Supreme Court cases can be looked upon, the Lahore High Court ruled in Crown v. Mohammad Sadiq Niaz that the magistrate has no authority to compel the investigation to be halted. It does not fall under their jurisdiction power.
In another case, S.N. Sharma v. Bipen Kumar Tiwari, the court held that section 156(3) of the Cr.P.C. can only empower a magistrate to order an investigation if the police had opted not to investigate the case.
And there is no further reference in the clause that a magistrate can also order a police inquiry to be halted under any section.
Hence, the clause plainly stated that the magistrate has no authority to stop or intervene in any ongoing police inquiry. The magistrate is not empowered to interfere in any inquiry that has already been initiated by the police.
The magistrate only gets involved when the police refuse to investigate. In this scenario, the magistrate has jurisdiction to direct the inquiry; otherwise, the magistrate has no control over the police's ability to investigate any matter. The police have complete power to investigate the matter independently.
We can deduce from the aforementioned references that a magistrate does not have the authority to halt a police inquiry, regardless of whether he has issued an order of investigation himself. The magistrate has no power in any condition to stop the investigation once it has commenced.