I'm still working on the manner of death for the clerics. Part of the investigation will look backwards through several centuries of suspicious deaths recorded in secret Vatican archives. However, I think I need at least another three deaths after the first three.
I believe I have a workable cause of death: sheer terror. No physical violence. I'm reading up on physiological changes that happen in the body in response to fear, and they're quite extensive. I'll amp up the blood test results to the extreme end of the fear spectrum. I don't know if a person can die from terror directly, or if they simply have a heart attack or stroke caused by fear. Probably one of the latter.
I'm thinking all of the bodies will be frozen by rigor mortis while kneeling, hands together in prayer. Naturally, that position should be impossible since a dead body can't hold that pose long enough for rigor to set in. I considered giving them an expression of terror on their faces with eyes wide, but I think most religious people who know they're about die would close their eyes and pray. There will be a smell of blood, because some condemned prisoners are known to sweat blood when they're about to die; there are about a hundred documented cases, although I still need to verify that (Jesus may have sweat blood at Gethsemane). I'll reread my sources to see if there are other outward signs of fear.
Thoughts?