I am the respondent in a minor claim in the Magistrates Court over the supply of a new driveway. My defence under evidence law is the Plaintiff's breach of contract, actual and implied, under contract law. I have withheld around 30% of the contract value and the plaintiff is attempting to recover that. Because of the low value the case will be heard without counsel. I know that the plaintiff has recently been convicted and heavily fined for False and Misleading Representations in regard to his concreting business. Can I bring this up in evidence to suggest he: a) Is not a credible witness b) Signed the contract with no intention of fulfilling the written terms on the contract, nor the implied terms such as compliance with Industry Standards and Council Regulations If so, how is this best done?