"A lawyer has no business with the justice or injustice of the cause which he undertakes, unless his client asks his opinion, and then he is bound to give it honestly. The justice or injustice of the cause is to be decided by the judge. Consider, sir; what is the purpose of courts of justice? It is, that every man may have his cause fairly tried, by men appointed to try causes. A lawyer is not to tell what he knows to be a lie: he is not to produce what he knows to be a false deed; but he is not to usurp the province of the jury and of the judge, and determine what shall be the effect of evidence — what shall be the result of legal argument."