Protecting the integrity of the force with regard to the decisions made in the farmhouse and the resulting consequences.
The desire and a sense of urgency to get relatives off their back.
Greed and alarm on the part of the relatives.
Openness to being corrupted by a relative.
Power: the fact that it was doable.
Lack of morals.
A combination of ignorance about Sheila and disdain towards Jeremy.
Protecting integrity by knowingly framing an innocent man thus putting the force in a worse position?
According to you, they had proof that Sheila was responsible - that would have gotten the relatives off their back.
The relatives had no power, especially if there was evidence of Sheila's guilt.
There is no motive for such openness.
Just because they could isn't really a convincing argument.
There wouldn't need to be ignorance towards Sheila if there was proof.