A more thorough explanation:

Lex Deraisnia is a legal term that means a law where someone denies an accusation because it doesn't make sense or is unlikely to be true.

• John was accused of stealing a car, but he denied it because he was out of town at the time. This is an example of lex deraisnia because John showed that the accusation was against reason.
• Susan was accused of cheating on a test, but she denied it because she had studied hard and knew the material well. This is an example of lex deraisnia because Susan showed that the accusation was unlikely to be true.

Lex Deraisnia is a way for someone to defend themselves against false accusations by showing that the accusation doesn't make sense or is unlikely to be true.