Leo hears Mona falsely accuse Nick of stealing from their employer The statement is defamatory?

Yes, Leo's observation of Mona falsely accusing Nick of stealing from their employer constitutes defamation. A defamatory statement is one that is false and harms the reputation of an individual. Since the accusation is untrue and could damage Nick's standing with their employer and colleagues, it meets the criteria for defamation. If Nick can prove the statement's falsity and the harm caused, he may have grounds for a defamation claim against Mona.