Did Walter give Martha and Sam away right at the start?

Are we supposed to know this, or is it deliberately ambiguous? Walter's father claims his son has told the police where to look, but Walter claims this is not the case later when talking to Martha. And a private investigator (I think) tries to take all the credit. It seems unlikely that Walter would defy his father, even though he does back Martha's story up later when he knows she's not telling the truth. So on balance I think he has betrayed her right at the start, but I'm not sure, and I don't know whether we are supposed to know either way.