Ethical concerns can jeopardize the outcome of the litigation, the lawyers’ involvement in the case, and quite possibly the lawyers’ continuing ability to practice law, should a disciplinary body become involved. Discretion is always appropriate in this context, whether you are raising or responding to the particular ethical concern. While it is impossible to generalize about ethical issues, the importance of addressing them promptly and ethically, and memorializing the resolution in writing, cannot be overstated.

From Letters for Litigators: Essential Communications for Opposing Counsel, Witnesses, Clients, and Others

http://www.abanet.org/abapubs/books/5150291