DR 5-101 Refusing Employment When the Interests of the Lawyer May Impair His Independent Professional Judgment.

1. Except with the consent of his client after full disclosure, a lawyer shall not accept employment if the exercise of his professional judgment on behalf of his client will be or reasonably may be affected by his own financial, business, property, or personal interests.
2. A lawyer shall not accept employment in contemplated or pending litigation if he know or it is obvious that he or a lawyer in his firm ought to by called as a witness, except that he may undertake the employment and he or a lawyer in his firm may testify:

1. If the testimony will relate solely to an uncontested matter.
2. If the testimony will relate solely to a matter of formality and there is no reason to believe that substantial evidence will be offered in opposition to the testimony.
3. If the testimony will relate solely to the nature and value of legal services rendered in the case by the lawyer or his firm to the client.
4. As to any matter, if refusal would work a substantial hardship on the client because of the distinctive value of the lawyer or his firm as counsel in the particular case.