Can the police ever arrest without a warrant?

If police have probable cause (a definable reason) to believe that a crime has been committed and that the suspect committed the crime, they can make an arrest without a warrant.  For example, a drunk driver who exhibits obvious signs of intoxication can be arrested on the spot without applying for a warrant.

There is one exception: The police must have a warrant to arrest a person at home if the arrest is for a nonserious offense and there is no fear the suspect will destroy evidence or cause harm to the public. An arrest warrant requires the police to provide to a judge a signed and sworn affidavit that provides facts to show probable cause that a specific crime has been committed and that the person named in the warrant committed the crime.