on being told by Jeremy that Mathew MacDonald was the hitman why does she never think to ask MacDonald weather its true or not.
Because she didn't know him. Or how to locate him.
And because she was with Bamber all the time after he whisked her over to WHF after a 5am phone call.
And Bamber told her MM was disappearing after the massacre.
And she told the police what she knew. They can find and ask MM. It's their job.
Next David will be saying the police should have wired up Julie after they had split up to try to get an audio confession from Bamber. Wait there...