This is most intriguing.
I will think how the walls and the victim could perceive different things…
P.S. I had to look up Roshomon :eek: :
'The interior narrative is of a trial wherein participants in a murder tell events as they saw them. The events they tell of involve a bandit tying up a samurai, having sex with his wife, and the samurai’s death by his own sword. The telling of these events varies from person to person, each of whom takes credit for the samurai’s death (including him). ’
Here’s what I did to some players in similar circumstances:
The victim was complicit in his own murder, his colleagues having promised to resurrect him. The players cast ‘Speak with Dead’, the victim framed somebody the bad guys wanted dead, and the players took the bait (and no, I never really let them know the truth).
I can’t remember first edition speak with dead (and those books are out in my garage) but I don’t recall the dead were obligated to be truthful.
Heh. Yep. Been running D&D campaigns (and other RPGs) for quite a while.
One of the top ten rules has got to be “think of the fastest, easiest ways to shortcut the game you planned and prepare a good reason why the players can’t use those methods.” 
Unfortunately, also in the top ten somewhere is, “And the players will always think of a way that you missed.” 
Glad to be of service.
I don’t suppose there’s any way you could get the walls to lie, too—like secretly replacing some of the stones with a cleverly disguised stone golem during routine repair, or something?
(I don’t know if that’d work under your rules, though—maybe Golems are too dumb, or won’t lie, or they’re too easily detectable, or they’re like a stealth bomber in terms of relative medieval cost.)
Have someone disguised as the keeped kill him. Stones don’t know any better and they’re probably not bright, so they will just say “He killed himself.”"
Keeper :smack: