Lying isn't as malicious as parents may think. Author Heather Shumaker says:
Young kids lie to express wishes and try to control their world. Your reaction matters more than her lie. What a young child "lies," she is doing her best to say the right thing. It's not a morality crises. She is trying to please you and protect herself. She is not purposefully dodging the truth to anger you and is not being "bad." Punishment doesn't stop lies (kids lie to avoid punishment). Instead, show your child that you like the truth, and she will alter her behavior to please you.