If Jeremy was as dissatisfied and covetous as some have made out; if he had considered and plotted in his own mind; if he was impatient and regarded Sheila as being 'better off dead' etc. (i.e. all the stuff that Steve and others peddle) - then why would he not regard a stated intention her part to kill her self, as the perfect opportunity to achieve his aims by proxy? So for example, he loaded the rifle and left it out for her, in the knowledge that something might indeed go wrong at the farm that night. Hence why he is perceived as feigning grief and not showing remorse in the wake of the killings; and perceived as behaving arrogantly and living the high life etc. Thinking he got away with the perfect crime because his sister actually did commit the killings. He would know the silencer was bogus - if he himself didn't leave it on the rifle (which would explain why he has fought against the sound moderator so hard all these years). He would be guilty of aiding and abetting killings having taken place, while at the same time, be a victim of being stitched up with bogus evidence and concealed facts.
She wouldn't need to 'coerce' him for assistance if it was his aim in the first place.
We peddle it because we see the threads of the tragedy are interwoven, in a family where admittedly two adoptees at various times wished members of their families dead. But it was Jeremy who started out by thinking of cyanide, of sleeping pills, and then the ultimate plan, which he had baulked at heretofore because he was so squeamish: they would all have to be shot and he would have to be the perpetrator.
He knew his sister's idle talk and her propensity to want to be granted an audience, something she had never been able to do at school, at work or at home. Therein the conversation with Helen Grimster, where she could hold court, now that she had driven Colin away through her lengthy conversations on the meaning of life and her smashing of pots to achieve a reaction-any reaction from any random human she encountered.
It's this progression in the crime which the Jeremy supporters fail to acknowledge, along with the temptation of an undivided inheritance which five deaths would bring. He, like his sister, had never felt in charge, a bystander rather than participant in events, anxious not to be exposed for the nonentity he really was. He had no real plans in the aftermath apart from furtherance in sexual conquest, though the money his wickedness brought him would have secured friends for a time until their patience ran out and he was left a solitary figure once more, a braggart with nothing left to brag about.
