Jeremy did have an alibi.
He said he was at home, 'sleeping like a log'. His downstairs phone rang, and rang, and rang (the answer machine had for some reason been switched off). Jeremy answered it, it was dad.
But how could Jeremy have been asleep if he had had rang Julie beforehand ?
He had no alibi. It was his word versus the Crown. Saying that,,his alibi will be in the public domain soon enough when it's found that someone rang him from WHF.
A phone ringing in the early hours would waken the dead,,so if Jeremy said he'd been fast asleep,then he was,prior to the phone ringing. It was while he was already up that he phoned Julie,,after the event,not before because she knew he'd be going straight to bed after having worked for 17 hours harvesting.