I was just wondering has anyone else realised that if the Ministry of Magic didn't believe Harry about Voldemort returning to power in the fifth book, could they not have just given him a few drops of veritaserum to see if he was telling the truth or not? It would have solved a few problems. Now that i've seen this i've started to realise other things - why couldn't they use veritaserum to prove that Sirius was innocent and Wormtail was guilty? Just give Sirius a few drops of Veritaserum and ask him if he murdered all those people - he has to tell the truth. Why couldn't they use veritaserum to find out which of the Death Eater's had truly been working under the influence of the Imperius curse? Just give the people under investigation a few drops of veritaserum and ask them if they had been working of their own accord - they have to tell the truth. To quote what Snape said in the fourth movie (I say movie because i'm not sure if he says it in the book aswell): "A few drops of this and the Dark Lord himself would reveal his deepest secrets". Looking at this we can assume that no-one could potentially resist the influences of veritaserum, seeing as the Dark Lord apparently couldn't. Be interested to hear your thoughts.

First off, the ministry did use veritaserum on harry, umbridge tries to give it to harry when she is questioning him. I am fairly sure that the way in which you recieve the veritaserum is important. Such as; if snape slipped veritaserum into harrys drink without him knowing than he would start spewing all of his secrets. However, if someone sat you down and said 'we are giving you veritaserum, now tell us all of your secrets' you would be able to control yourself. So, if the ministry used veritaserum to solve crimes and find guilt or innocence the people on trial would know that they are receiving it and it would not have as much of an effect on them. It's the same case with Harry, if he would have drunk veritaserum he may have been able to fight off the desire to tell the truth. Its the same reason they dont just use legilimency on criminals because a skilled occlumens could block the images or even change them to show that they were innocent when they actually weren't

This can't be right though. I was re-reading the sixth book and I came across this:

This shows that the Ministry does actually use Veritaserum to try and pry the information out of criminals. They wouldn't do that if it was resistable. So clearly Veritaserum isn't something resistable even if you know your taking it. Be interested to hear what you think.