This is a great question. A lawyer has to follow his or her own conscience, but also follow the law. Even if you know that your client is guilty, you are still responsible for representing him or her to the best of your ability. That can be hard when you find the person’s actions morally repugnant.
I respectfully and vigorously disagree with the above post. The Attorney's oath (at least that to which I swore when I was admitted to the bar) states in part:
I will never reject for reasons personal to myself, the cause of the defenseless or the oppressed, or delay any man's cause for lucre or malice.
The Canons of Ethics are crystal clear that an attorney's opinion of the guilt or innocence of his client is not a determinant. It that were the case, no person accused of a heinous crime would ever be able to retain counsel, or expect a vigorous defense. It should be pointed out that John Adams represented the British soldiers accused of manslaughter in the Boston Massacre because of his personal belief that everyone is entitled to an attorney, regardless of his perceived guilt or innocence. Similarly, Clarence Darrow represented Leopold and Loeb in the face of overwhelming evidence.
The quote above is misguided. It does not refer to an attorney's personal conscience when representing a client; but rather indicates that he/she should represent his/her client "zealously within the bounds of the law," to quote the relevant Canon of Professional Ethics.
In twenty years as a practicing attorney, there were many occasions when I represented one whose innocence I doubted. Some of those instances involved a paid retainer, other times I was appointed to represent the defendant by the court. Never did I--or any attorney worth his salt of whom I am aware--refuse to represent a client simply because of personal doubts. Only in instances in which he is too involved with the matter to render independent judgment should he step aside. If matters of conscience prevent lawyers from taking cases, then perhaps we must revert back to the days of the Court of Star Chamber.
This is a fantastic question. Lawyers should always seek to uphold the highest level of ethical standards. For this reason, a lawyer should not take a case where he or she must compromise his or her sense of morality. Unfortunately, many lawyers do not follow this commonsense ethical practice. The Preamble to the Model Rules of Professional Conduct states the following in no ambiguous terms:
"A lawyer is also guided by personal conscience and the approbation of professional peers. A lawyer should strive to attain the highest level of skill, to improve the law and the legal profession and to exemplify the legal profession's ideals of public service."
With that stated, the lawyer's job is also represent someone to the best of his or her ability. In order to do this, a lawyer must be able to set aside judgment, and represent his or her client based on the law. If a lawyer does this, then he or she can be stated to have a clear conscience, because he or she has done what is expected.