I have yet to find anyone willing and or able to be of assistance.
I suspected there was merriment of some sort being pursued, and when that occurs, illegal drugs and alcohol seem to be present.
There is far too much of this that occurs, and too many people die prematurely because of poor choices by others.
That said, why not talk to a couple private investigators?
Start looking around and find three that seem capable.
Then meet with the investigators, and see what you can learn.
If you dislike all three, look for three more.
In any situation such as yours, the RIGHT private investigator might be able to obtain the missing pieces that can possibly bring you some enlightenment.
I know you will not obtain the peace you desire, as only time can do that for you.
We all know the pain death can bring to others, few know the unbearable pain that the murder of a love done brings.
For every life taken at the evil devices of a murderer, studies tell us that 150 to 200 people grieve that loss.
I know that I'd do everything I could to obtain all the facts and facets of who did what if some savage murdered my mother.
God bless, and I wish you peace, mate.