lie through one's teeth - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, lie in one's teeth. Utter outrageous falsehoods, as in He was lying through his teeth when he said he'd never seen her before; they've known each other for years. This expression presumably alludes to a particular facial grimace one assumes when lying. [c. 1300]