Veritaserum - Entirely Effective?

[Pepper Imp]

Here's what the Lexicon has to say on the potion:

Veritaserum:

The most powerful Truth Serum available, this colourless, odourless potion (which looks like plain water) forces the drinker to tell the truth.

A Truth Potion so powerful that three drops would have the drinker spilling his or her innermost secrets.

Use of this potion is controlled by very strict Ministry guidelines.

(...)

An alert wizard who's good at Potions can protect himself against the use of Veritaserum by keeping some antidote handy.

I was wondering if this potion was entirely accurate - is it possible for someone to protect their secrets by believing something actually happened?

For example, if Luna believed that Harry was at dinner, but he was in the Common Room, would she tell the truth or the truth as she sees it if she was given Veritaserum?

Thanks,
Cammie!

[SiriuslyMental]

Yes. The entire point of Veritaserum is that you tell the truth. If, to you, the truth is something that was planted into your mind, etc, it's most likely you'd tell that under Veritaserum.

[Sour.Apple.]

I'd say the truth as she sees it, because then she truely doesn't know where Harry is. If it worked like that, then when the Ministry was searching for Death Eaters they could have just given some Veritaserum to one of thier workers and asked them where the Death Eaters are. Or, Harry could have given some to Hermione and asked her where the Horcruxes are.

See how they sounds almost too easy?

[Pepper Imp]

Thanks for the very prompt replies! *hugs*

I see what you guys mean - I thought the same thing, but wanted it confirmed!

Thanks again,
Cammie!

[Dark_Lady_Z]

"It is Veritaserum- a Truth Potion so powerful that three drops would have you spilling your inner most secrets for the entire class to hear"

---Snape (Goblet of Fire)

[Lobena Bricatta]

Ok so here it is
I have been looking for that answer to and I found it on the Wikipedia Harry Ptter portal, Here are the words by JKR Herself

Section: F.A.Q.
Veritaserum plays a big part in finding out the truth from Mad-Eye Moody in book four. Why then is it not used for example in the trials mentioned in the same book? It would be much easier in solving problems like whether Sirius Black was guilty or not?

Veritaserum works best upon the unsuspecting, the vulnerable and those insufficiently skilled (in one way or another) to protect themselves against it. Barty Crouch had been attacked before the potion was given to him and was still very groggy, otherwise he could have employed a range of measures against the Potion - he might have sealed his own throat and faked a declaration of innocence, transformed the Potion into something else before it touched his lips, or employed Occlumency against its effects. In other words, just like every other kind of magic within the books, Veritaserum is not infallible. As some wizards can prevent themselves being affected, and others cannot, it is an unfair and unreliable tool to use at a trial.

Sirius might have volunteered to take the potion had he been given the chance, but he was never offered it. Mr. Crouch senior, power mad and increasingly unjust in the way he was treating suspects, threw him into Azkaban on the (admittedly rather convincing) testimony of many eyewitnesses. The sad fact is that even if Sirius had told the truth under the influence of the Potion, Mr. Crouch could still have insisted that he was using trickery to render himself immune to it.

All rights reserved JK Rowling.

Hope it helps