For some reason it's a common belief that it's impossible to lie when you are hypnotized. If that was the case I'm pretty sure we would see a lot of witnesses being hypnotized to make sure they didn't lie in court. But it is very easy to lie in the hypnotic state, you can decide exactly what you want to say in response to any questions the hypnotist asks you.

It is also quite easy to make it look like you are hypnotized. So even if it wasn't possible to lie in hypnosis, there would still be the possibility to fake the hypnotic state, and then lie. That it's possible to lie in hypnosis makes it useless as a testimonal in court. But that doesn't mean that hypnosis cannot be used by the law enforcement. Since the subconscious mind holds every experience in mind, the law enforement sometimes uses forensic hypnosis to question witnesses for number plates, they may only have seen in a split-second. There is no doubt that investigation is much easier if you have a suspect and/or a getaway car. Wether such details can be recalled by the subject greatly depends on the situation and the skill of the forensic hypnotist.

The conclusion: You can lie as much as you want in hypnosis, but you should ask yourself why you would want to lie, and if this reason is good enough. Most hypnotists promise to keep the consultation secret.