In Supernatural, Sam and Dean both have anti possession tattoos over their hearts.
But, in Season 3 Episode 12, "Jus in Bello", the Winchesters gave Nancy Fitzgerald, a secretary, a necklace of an anti possession symbol, which ultimately had the same effect of the tattoo.
Does the symbol (tattoo or otherwise) have to be directly over the heart to work? Or could it be placed somewhere else, like a wrist or ankle and have the same effect?
No, an anti-possession mark doesn't have to be over the heart. In season 8, Kevin and his ninja mom, Linda, got them on their arms - but if you remember, Linda's was burned off so that Crowley could possess her.
To make it virtually impossible for anyone to possess the Winchesters, Cass put Sam and Dean's anti-possession marks, visibly, over their hearts, but there was mention that he had marked them deeper, at the very least the markings went through to their rib cages, but it makes sense that the marks actually went all the way through to their hearts. Besides the symbolism (and convenience since the scene would have been very different if he'd reached down and grabbed them by the ankles instead of placing a hand on each other their chests), the basic anatomy would just be too much to burn off or out if the marks were placed that deep. In other words: Burnt/removed ribs + burnt/removed heart = No decent meat-suit to walk around in, so no reason to even bother trying.
Nope. Kevin and Linda got them on their forarms in season eight, and we know they worked because Linda's later had to be burned off so Crowley could possess her.
