Legal Question in Criminal Law in New York

Police usually don't need a warrant to make an arrest, but they usually do need one to enter someone's home unless an occupant gives them permission. There are a variety of reasons, though, why police might be able to enter without permission and without a warrant. Whether this particular arrest was proper will depend upon the facts.

The police must have probable cause to make an arrest, Just being a suspect is insufficient. Unless danger is apparent, the police must obtain a warrant.

Unless there is some emergency or hot pursuit, the police cannot enter a private residence to make an arrest without a warrant or permission of the owner or person in charge. But it does not nullify the arrest. The only real penalty is that any evidence seized or observed would be suppressed in the case.