There is clear evidence that marks on the aga surround were deliberately made on 11th September 1985, and that a silencer which was used to make those additional marks, did not get sent to the lab' to be checked for blood and fibres, until 20th September 1985 - a presence of this paint from the aga on the silencer was used to secure the convictions for these murders...
Jeremy is only convicted of the murders by verdict of a jury based on false evidence, it does not mean that he killed anyone, it only means he is convicted, in the same way that those who are found not guilty, could have committed the crimes they were found not guilty of?
What matters is the quality of the evidence used by the prosecution to secure the convictions, convictions would only be valid if the evidence used was above suspicion, and not dodgy ...