Well there are 17 pieces of evidence linking Bamber to the crime. This is because the evidence which shows it couldn't be Sheila, links Bamber, courtesy of Bamber's call to the police.
Evidence placing Bamber at the scene -
The silencer.
The bible landing on top of Sheila's blood.
Sheila's legs being pulled after the second shot.
The 14 reasons why Sheila could not have committed the massacre.