Except as provided in paragraph (b), a lawyer shall not represent a client if the representation involves a concurrent conflict of interest. As a representative of clients, a lawyer performs various functions.As advisor, a lawyer provides a client with. With the organization against a claim arising out of an alleged violation of law. NO, you can't call opposing counsel to testify! Include dates, the nature of the legal matter, and specific information about what you feel the attorney did wrong. Yes it is required to provide your documents etc. , to the opposing side, that you are planning to use in trial to support your case. Massachusetts Bar Foundation and the Massachusetts Legal Assistance. A judgment of guilt against a criminal defendant. Counsel.