From the cited article:
But a new report by Lucien Haag of Forensic Science Services in Arizona states that the trigger 'had to be pulled or depressed sufficiently to release the fully cocked or retracted hammer of the evidence revolver.'
I'm not so sure about the relevancy there because of the "fully cocked or retracted" qualification.
Isn't it possible to withdraw the hammer not-quite-to-the half-cock-notch, then let it slip from the thumb so that it strikes the primer, albeit lightly? Without using the trigger.
I don't have any SA revolvers any more so I can't test this gun-in-hand, but I don't think the cylinder has rotated yet under this situation. I think the pawl must be just barely peeping out of the recoil plate without rotating the cylinder.
It would be a light primer strike, but if the operation were repeated a number of times, I can see it setting off the primer. Sort of like hangfires, where if you cock and "fire" again, they may go off.
Nevertheless, as I say, "never point a gun where you can't fix the hole."
Terry, 230RN