Another related thing: When you hover the cursor over the skull you see the cause of death. "In suspicious accident" is pretty obvious, successful murder plot or paid assassination in which the plotters were not caught (although the culprits might often be very obvious ones). The other thing is "Murdered by orders of nn" which was discussed already, the name in NN might have not been the main plotter but any plot member, who has got the blame (may have been framed or just the only one who got caught)
What about "Died in an accident"? Are these genuine accidents or very very successful outcomes of murder plots? I mean like suspicious accidents which have been set so well that they don't even rouse any suspects (a paradox, I admit)?
I don't think my character has ever died in a genuine accident. I have got injured in a hunting accident ("Maimed" trait outcome and died shortly after) but haven't got the outright death result. Are there any other genuine accidents in the game or have I just missed them completely? In any case when I see "Died in an accident" I get a little suspicious...
Deaths in accidents are deaths the likes of which you see when you magnificently fail at slaying that boar for your feast.