lawyer-witness rule

The principle that prohibits an attorney from serving as an advocate and a witness in the same case. Also known as the advocate-witness rule, it keeps attorneys from being placed in a situation that could at best create a conflict of interest for both themselves and their clients. It also keeps adversary attorneys from having to cross-examine opposing counsel in front of a jury at trial. Attorneys are allowed to serve as witnesses if their testimony is about factual matters that have no bearing on the case; likewise, they are allowed to remain as counsel if their removal from the case would create a substantial hardship for the client. The rule does not prohibit attorneys from being witnesses in general, nor does it prohibit an attorney-witness from assisting in a client's case, for example by acting as a consultant or attending depositions.