Veritaserum is a powerful truth serum. The potion effectively forces the drinker to answer any questions put to them truthfully, though there are certain methods of resistance. Use of this potion is strictly controlled by the Ministry of Magic.
Veritaserum was used on Barty 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 earlier that year because he suspected that Harry had been stealing supplies from his storeroom necessary to brew Polyjuice Potion. This was prior to the discovery that Barty Crouch Jr. was in fact the one who had been stealing the ingredients to keep up his disguise as Alastor Moody.
Dolores Umbridge attempted to use Veritaserum on Harry the following year, but to no effect. In actuality, Snape had presented her with a fake potion, and Harry only pretended to drink it, instead dumping it in one of her plants while she was occupied. Umbridge later asked for more Veritaserum after Harry broke into her office to contact Sirius Black, but Snape said it would take a month to make more. Instead, he suggested she use poisons on Harry if the situation were very grave. Snape also taunted her about using the entire bottle during one dosage rather than using the necessary three drops. As a result, Dolores suspended Snape and tried to use the Cruciatus Curse on Harry. However, Hermione Granger, who was also present, intervened and pretended to tell Umbridge the truth, thus sparing Harry from the curse.
At the beginning of the 1995–1996 school year, Horace Slughorn, the Potions master, brewed Veritaserum as an example of the type of potion they should be able to make after completing their N.E.W.T.S. Later, Harry suggested using it on Slughorn to collect a memory. Dumbledore discouraged this idea since he knew that Slughorn would not be fooled easily and could resist the potion with an antidote. Additionally, Dumbledore did not want to use force or coercion on the Potions master, as betraying his trust in such a way would most likely result in his memory never been collected by Harry.
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 pretty much any drink, and three drops are a sufficient dose to make the drinker "spill out his innermost secrets". Thus, the potion forces the drinker to tell the complete truth to any question put to him/her, according to what the drinker perceives as true.
For the same reasons Muggles don't use polygraph tests in court, Veritaserum is no more reliable than its Muggle counterpart. Since some wizards and witches can resist its effects while others cannot, Veritaserum is "unfair and unreliable to use at a trial" and would be difficult to use as definite proof of guilt or innocence.
Another problem is that the victim states what only they believe to be true, so the victim's sanity and perception of reality also factors in during interrogations. Therefore, while the drinker's answers are sincere, they are not necessarily true. This is the main reason why Barty Crouch Jr.'s testimony was only partially credible, as some of his answers were true in his mind, but known to be false by his interrogators; Cornelius Fudge believed that Crouch being a "raving lunatic" as a mitigating factor on the Veritaserum's full effectiveness, thus chose not to believe half of it.
The name comes from the latin veritas, meaning "truth," and the Latin serum which means "fluid" or "liquid."
Behind the scenes
- In the film version of Harry Potter and the Goblet of Fire, Snape says that Veritaserum would make even Voldemort spill his darkest secrets. This is most likely an exaggeration meant to intimidate Harry, as Occlumency can be used as a defence against it. However, in the book Snape merely states that it would make Harry spill his innermost secrets, which would almost certainly be true (though Harry's resistance against the Imperius Curse could indicate otherwise).
- In 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 the the last of the Veritaserum on Cho Chang to force her to betray Dumbledore's Army by exposing the location of their meeting place, the Room of Requirement. Marietta Edgecombe, who betrayed the D.A. in the novels, was omitted from the film. Cho's unwilling betrayal was also the cause of her split with Harry Potter in the film, as Harry was unaware that Cho was under the influence of Veritaserum until revealed by Snape in a conversation with Umbridge; in the novel, it was her continuing grief over Cedric Diggory, irrational jealousy of Hermione Granger, and defence of Marietta's betrayal.
- Because of the potion's usage being heavily controlled by the Ministry, the usages over the series are unauthorised and/or illegal: Dumbledore did not acquire permission from the Ministry before using it on Crouch, Umbridge used it for interrogating students despite such action being forbidden (though being a high-ranking Ministry official herself, she may have had the authority then), and Skeeter used it on Bagshot for an interview.
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.
- Harry Potter and the Goblet of Fire (First appearance)
- Harry Potter and the Goblet of Fire (film)
- Harry Potter and the Order of the Phoenix (Mentioned only)
- Harry Potter and the Order of the Phoenix (film) (Mentioned only)
- Harry Potter and the Order of the Phoenix (video game) (Mentioned only)
- Harry Potter and the Half-Blood Prince
- Harry Potter and the Half-Blood Prince (film)
- Harry Potter and the Deathly Hallows (Mentioned only)
- The Queen's Handbag (Mentioned only)