Δαφνη Ευτυχια Αρθουρος

I think you're right and they're wrong.

"Alleged criminal" or "alleged robber/arsonist/etc." works.

The "is it a crime" situation is one place where there's room for phrasing like "alleged arson" or "alleged crime"--for example, the mere statement by a police officer, building owner, or insurance company investigator that a fire was arson doesn't prove that it was. (And "there was no crime" is a possible defense against an accusation, even if an indictment has been brought.)