What phenomenon was believed to provide evidence of vampires being real during historical times?

The belief that blood pouring out of the body provided evidence of vampires being real is rooted in historical interpretations of certain bodily phenomena associated with death and decay. In many cultures, when a person died, the post-mortem processes sometimes led to blood being expelled from the body, which could be interpreted as a sign of a vampire's influence, especially when viewed through the lens of folklore. This connection between blood and the undead became a cornerstone of vampire mythology, fueling the idea that an undead being could rise from the grave and cause harm to the living, often represented through the imagery of blood.

The other options do relate to vampire lore in various ways but do not carry the same direct link to physical evidence. The presence of garlic is often considered a protective measure against vampires, rather than an indication of their existence. Unexplained deaths could invoke suspicion, but they could also stem from various natural causes without implicating vampires specifically. Shadows in the moonlight might evoke a spooky atmosphere associated with supernatural folklore but lack a concrete association with actual evidence of vampire activity.