Sparks, if Jeremy hired a hitman to kill five people, including two little kids, (yeah right!), for 2000 £, (more yeah right!) why didn´t he make sure to have an airtight alibi? That is elementary - and one of the reasons people hire killers: to make sure that they can prove that it was impossible for them to have been at the murderscene.
Jeremy was home alone, sleeping. Not much of an alibi.