§ 199 Authority must be stated on arrest without warrant, when.

If a police officer arrests someone without having a warrant, the officer has to tell that person two things: that they have the authority to make the arrest, and why the arrest is happening. This gives the person being arrested basic information about what's going on and why they're being taken into custody.

There are two exceptions to this rule. The officer doesn't have to explain their authority or the reason for arrest if the person is caught in the act of committing a crime. The same is true if the officer is chasing someone right after they've escaped from custody. In both situations, the reason for the arrest is already obvious, so there's no need for the officer to spell it out.