The standard wording used by the police in this country when arresting someone is "I am arresting you on suspicion of . . . ".
It's irrelevant as to whether or not the police officer has just witnessed that person gunning down a dozen people or driving erratically while swigging from a bottle of vodka. An arrest is always made solely "on suspicion of . . .".
So everyone who is arrested here is always a 'suspect', irrespective of the strength of any evidence against them.
OK, thanks, Buenchico. I thought that if a person was suspected of committing a crime they were considered to be a "person of interest" and taken in for further questioning and held for a defined period of time pending further investigations.