There would be no reason to move June from the bed and I'm willing to accept that by dint of her own efforts she had managed to move out of bed and was finished off with two shots right between the eyes,which is where the DNA may have come from. What does Jeremy say about the silencer? Did Sheila walk over her mother to get to the far side of the master bedroom,necessitating her getting blood on the soles of her feet? If Jeremy is the guilty party he has to bring Sheila out of her bedroom or forensics would be able to prove she had never left that location and therefore could have taken no part in the killings.