Some teens believe if they protest their innocence long enough, parents will begin to doubt themselves, but that's not going to happen... not in this parental circle.
"I think parents have to deal with lying the way a cop deals with speeding. If you’re going too fast, he gives you a ticket. He’s not interested in a lot of explanations from you. He’s just going to give you a consequence. Look at it the same way with your child. He didn’t tell the truth, whether the truth was distorted, omitted or withheld. There should simply be consequences for that. The first time you lie, you go to bed an hour early. The second time, you lose your phone. It should be something that the kid feels. You lose your phone for twenty four hours. You lose your phone for two days. You lose computer time or TV time.One of the hardest lessons teen may not learn until they are one day a parent is that the trust that is violated by lying is very slowly and difficultly won back.
The consequences have to make the child uncomfortable or they don’t change anything. The idea is that the next time he’s faced with telling you the truth or lying, he’ll recall how uncomfortable he was when he did the consequence for lying, and he’ll tell you the truth instead." (source)