"...An Irish CID spokesman said on the radio yesterday that there was no question of the force 'looking to interview anyone else concerning her death'.

That says they know it was him in a roundabout way.

Unfortunately that is precisely what has been said by police (and accepted by commentators) in cases where things have turned out that they were wrong. Including cases where subsequent evidence has led to other people being convicted, and the original accused completely exonerated. For example the Rachel Nickell murder