The willful telling of a lie after being sworn to tell the truth under penalty of perjury is a crime
Perjury can be difficult to prove since it is based on the defendant’s state of mind.
The perjurer must know he is lying and do so intentionally. Committing perjury is a crime.
Sometimes the liar can have a cognitive disability or memory loss, which prevents the accused from adequately recalling events with sufficient specificity. This happens in civil litigation where a witness or party is under oath during a deposition.
For example, a person with dyslexia who has a history of problems with the sequence of events or is prone to mix numbers up in his mind may have difficulty with recall without any intent to falsify his testimony.
If the defendant’s disability had been diagnosed well before being accused of the crime of perjury, and if the disability had been formerly medically substantiated, then the defendant would be able to claim that it was there a neurological condition that made it difficult to process his thoughts to give accurate testimony at the time of trial.
In a criminal contempt trial, it is possible that this criminal defense would likely constitute reasonable doubt in the jury’s minds. Under these circumstances, the prosecutor would likely reconsider prosecuting the case.
Sometimes, a divorcing party will hide property during a divorce proceeding and is then caught having committed perjury regarding ownership of the property. This is an example of criminal contempt.
The federal crime of perjury is detailed in 18 U.S. Code Section 1621
