"Detained" is not the same as "arrested", although it may look and feel about the same. So the Mosul chief of police may have been correct in a technical sense. Nick Berg was not "arrested", but he probably spent several days in custody, primarily for his own protection.
But the password? Too improbable. Berg may have not exercised the necessary caution in protecting the password, but to say that he gave it up willingly to Zaccarias Moussaoui just strains credulity too far.
Sounds like the Mosul police chief at best is attempting to play word games. The US spokesman Dan Senor said that Berg was "arrested" on March 24 by the police. The police chief's statement that he knew nothing about the case also stinks to high heaven.
We've got contradictory statements by the US and Iraqi officials and the know nothing statement by the police chief is just a little hard to swallow.