Why do you believe the police created the industrial frame department?
Do you believe the relatives or police fabricated the silencer?
What order do you believe Sheila killed the family?
I don’t know what an industrial frame department is. The conspiracy to convict Jeremy would have consisted of a few people, with Ainsley masterminding the plot. Many others who provided evidence may not have realized that they were contributing to the framing of Jeremy.
A combination of the relatives, primarily RWB, with the implicit approval of Ainsley.
In my opinion Sheila killed the twins, then June and finally Nevill but I don’t suppose that will ever be known for certain.