What is the test for reasonable grounds for entry and search of an apartment for persons under the circumstances of an arrest?

Sergeant Curts acknowledged that while he suspected that someone else was in the apartment, he did not have reasonable grounds to believe that someone was in the apartment. He went no further than to say there was a possibility that someone else was in the apartment. The trial judge appears to have held that a possibility was not enough to justify the entry and search. I disagree. The exercise of a police power ancillary to an arrest does not require independent grounds for its exercise: Cloutier v. Langlois at p. 278. If the circumstances of an arrest give rise to a legitimate cause for concern with respect to the safety of those at the scene, reasonable steps to allay that concern may be taken. The nature of the apprehended risk, the potential consequences of not taking protective measures, the availability of alternative measures, and the likelihood of the contemplated danger actually existing, must all be considered. The officers making this assessment must, of course, do so on the spot with no time for careful reflection. In my opinion, a reasonable suspicion, based on the particular circumstances of the arrest, that someone is on the other side of a closed door with a loaded sub-machine gun, or that someone is lying injured on the other side of that door, creates a legitimate cause for concern justifying entry and search of the apartment for persons.