The way I see it is this..
The jury are likely to accept that on the day Preston was killed
- JV assaulted Preston orally which stopped him breathing and by forcible penetration that caused serious bowel injuries, abnormalities to his bum and bladder injury..
To find JMF innocent
- they’ve got to believe that on the day that Preston is photographed hanging on his neck turning blue over the cot bars, with again a very damaged
mole, with semen falling from his mouth on the exact location that is then tested to show JMF sperm in a MIXED sample with Preston’s dna, that JMF was there that whole day and his sperm is there just as terrible bad luck for the clean freak. It’s just a coincidence that the evidence of this assault totally mirrors that of Preston’s death and JMF is there the whole time along with his sperm
They’ve also got to believe JMF’s account that he really did come home to find Preston still sitting up being sick when in fact he had been filmed an hour and a half before at near death not breathing for 20+ seconds at a time, gasping and grunting and that all pathology shows he had been clinically dead for some time before arrival at hospital. He did not lost consciousness just as they got in the car which is what they both claim.
Now unless JMF says he lied about that to protect JV, why else would he need to lie? Because he knows he participated in these attacks previously too and it makes it look more convincing that he had no idea Preston was being tortured all day by JV if he carries on with the fiction of the scene he arrived to when in fact Preston was dead.