Police are responsible for spreading this false rumor, which as timed moved on, became an accepted fact, but the truth of the mater is that Jeremy has never accused Sheila of killing anyone, or herself - it was the prosecution who put the case to the jury that it could only have been Sheila or Jeremy, but as we now know some evidence did exist which was not raised before the jury that Jeremy accused the police of killing everyone...
In view of Jeremy's accusation which he made to a police officer immediately upon being told that all his family were dead, the jury should have been given the choice of (a) Sheila, (b) Jeremy, and or (c) the police?
If Choice (c) had been given to the jury, and the allegation made by Jeremy to PC Oliver at the scene, that the police had shot and killed his family, the court would have looked into the possibility that the crime scene had been stage managed by the police before pictures were taken, and not that Jeremy had stage managed the scene himself...
Jeremy Bamber got blamed for doing things at the scene, which the police were/are responsible for doing, and by blaming Jeremy for doing the things which the police did, it made it look more likely that Jeremy killed everyone including his sister, and that he was the one who had done the stage managing...
If option (c) had been an issue at the time of the trial, I am positive that with all the evidence now available that the court would have been persuade that it was the police who stage managed the scene, not Jeremy, or anyone else...
It should also be pointed out, that during his summing up speech, Justice Drake told the jury that the killer had to be either Sheila or Jeremy and that there was no suggestion that anyone else could have been responsible, but we now know that Jeremy accused the police of shooting dead his family, and with this in mind, this was evidence of a possible third party involvement, which was relevant to the case, and which should not have been kept back from the jury...
In effect...
The trial judge misdirected the jury on that point...