From Longman Dictionary of Contemporary Englishblind alleyˌblind ˈalley noun [countable] 1 TTRa small narrow street with no way out at one end2 NOT DO somethinga way of doing something that seems as if it will have a successful result, but which in fact does not False information has led the police up a series of blind alleys.
Examples from the Corpus
blind alley• The echinoderms may seem, from a human point of view, to be a blind alley of no particular importance.• Al said the talks had temporarily gone down a blind alley, but he was sure the two companies could agree.• If the police went charging up a blind alley as a result of her information, it wouldn't be her fault.• It took the reader down every blind alley. 