The landlord brought an action against the defendant, Su-Chen Wu Yang , as guarantor on a commercial lease. The defendant, as the director and shareholder of the tenant corporation, admitted she had signed the lease as co-covenantor, but relied on non est factum, asserting that her interpreter told her that the lease did not contain a personal guarantee.

The defence succeeded because the defendant had constantly taken the position that she did not want to provide a personal guarantee and had been assured she was not assuming any personal liability under the lease. The landlord was careless in relying on the translator to communicate its position on a critical term in the lease to a non-English signatory, and the landlords actions on the guarantee was dismissed.

Should a person who signs a contract be able to raise non est factum? does this doctrine reduce commercial certainty and security? should courts simply require individuals to bear more responsibility for their own mistakes?