Hold tip of wand to targeted wand
Prior Incantato is the incantation of a spell that, if pointed at a wand, can show the last spell performed. It was used by Amos Diggory to learn whose wand had been used to cast the Dark Mark at the 1994 Quidditch World Cup.
Difference with Priori Incantatem
The Prior Incantato spell could be confused with the Priori Incantatem effect triggered by wands sharing a common core when they are forced to duel with each other, but also induced by analytical spells. The Deletrius Charm can erase the shadow produced by this spell.
Latin prior, "previous", and incantate, "to speak a spell" (past participle incantatum).
Behind the scenes
- In Harry Potter and the Deathly Hallows: Part 1, during the Skirmish at Malfoy Manor in 1998 Bellatrix Lestrange used this spell on Hermione Granger's wand to learn if she used a Stinging Hex on Harry Potter to make him unrecognizable.