be untruthful

References in classic literature ?
She was ashamed of being irritated from some cause she could not define even to herself; for though she had no intention to be untruthful, her reply had not touched the real hurt within her.
There are a slew of presidential statements going back to 2008 which subsequent evidence has shown to be untruthful.
Singer pointed out a jury instruction that says that if a witness is thought to be untruthful in one part of his testimony, that witness's entire testimony can be discarded.