I am just wondering what decisions, or group decisions would make anyone else in a group liable in the event of an accident?
An accident is just that! How could the owner/s of an aircraft be liable?
A fault with the aircraft?
Given the new contractual arrangments with EASA Part M its fairly clear who is responsable for what, where, when and how. If you keep your end up of the contract you should be bullet proof!
A fault with the pilot?
All the usual stuff - Medical, Licence ,Class rating, currency, flying within the licence, rules of the air, weather etc. If all this is good the pilot/ estate should be bullet proof!
Anything else is an act of god or an ACCIDENT!
If you have the right people in your group you should be ok - good luck with it