Veritaserum

"Three drops of this and even You-Know-Who himself would spill out his innermost secrets."

- Severus Snape threatening Harry Potter with Veritaserum.

Veritaserum is a powerful Truth Serum that is most commonly used in interrogation. The potion effectively forces the drinker to answer any questions put to them truthfully, though there are some difficult methods of resistance. Use of the potion is strictly controlled by the Ministry of Magic.

Description and Effects
Veritaserum is clear, colourless, and odourless and is almost indistinguishable from water. According to Severus Snape, the potion must mature for a full lunar phase, and is quite difficult to produce. It can be mixed with any drink, and three drops are a sufficient dose to make the drinker "spill out their innermost secrets", although this is only a example to say that it forces the drinker to tell the complete truth to any question asked to him/her. It can be resisted through different methods, including the taking of the antidote and Occlumency.

Known Uses
Veritaserum was used on Bartemius Crouch Jr. in June of 1995, when Albus Dumbledore discovered that Crouch was disguised as the Defence Against the Dark Arts teacher, Alastor Moody. Severus Snape also threatened Harry Potter with it in the same year, suspecting that Harry had been stealing supplies necessary to brew Polyjuice Potion prior to the discovery that Barty Crouch Jr. was the one who stole the ingredients to disguise himself as Alastor Moody for Lord Voldemort's plan.

Dolores Umbridge attempted to use Veritaserum on Harry the following year, but to no effect, (apparently because Snape had presented her with a fake potion) and because Harry only pretended to drink it, he dumped it in one of her plants while she was occupied. .Also, Umbridge asked for more Veritaserum on the same year after Harry broke in her office to contact Sirius Black. But Snape said he need to make more and suggested her to use poisons on Harry if the situation was very grave, but Dolores gave up on him, and proceeded to tell Harry the Cruciatus Curse would have to do, but Hermione Granger, who was also present, intervened and pretended to tell Umbridge the truth.

Rita Skeeter used Veritaserum on Bathilda Bagshot while interviewing her about Albus Dumbledore and his family for her biography of him.

Because some wizards and witches can resist its effects and others cannot, Veritaserum is an "unfair and unreliable to use at a trial", and thus cannot be used as definite proof of guilt or innocence. Another weakness is that the victim only states what they believe to be true, so the victims sanity and perception of reality also factor in during interrogations. This is the main reason why Barty Crouch Jr.'s testomony was not credible, as he was clearly insane. .

Etymology
The name comes from the Latin veritas, meaning "truth", plus serum which means fluid or liquid.

Author's Comments
J.K. Rowling has said that Veritaserum "works best upon the unsuspecting, the vulnerable and those insufficiently skilled (in one way or another) to protect themselves against it...just like every other kind of magic within the books, Veritaserum is not infallible". For this reason, she explained that even if Sirius Black had been given the opportunity to testify to his innocence under Veritaserum, the Wizengamot likely still would have found him guilty by claiming that Sirius was using trickery to be immune to it.

Behind the scenes

 * In the book version of Harry Potter and the Goblet of Fire, when Barty Crouch Jr. was being interrogated at the end of the year, Dumbledore shook three drops of Veritaserum into his mouth while he was unconscious. In the film version, Snape poured the entire contents of the bottle right into Barty's mouth while it was forced open in a struggle.
 * In the film version of Harry Potter and the Order of the Phoenix, Dolores Umbridge used Veritaserum on Cho Chang to force her to betray Dumbledore's Army by exposing the location of their meeting place, the Room of Requirement. The character who betrayed the D.A. in the novels, Marietta Edgecombe, was omitted from the film. Cho's unwilling betrayal was also the cause of her split with Harry Potter in the film, whereas in the novel, it was her continuing grief over Cedric Diggory, unreasonable jealousy of Hermione Granger, and defence of uninnocent Marietta.

Appearances

 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Deathly Hallows