Joseph,
An attorney must advocate for the best interests of his/her client.
Again, as I have repeatedly said: I do not do criminal work.
That said, a good attorney will NEVER ask his client accused of murder if he/she committed the act.
There is NO requirement that a defendant ever take the stand as a defense witness (and they are not generally called by the prosecution).
If a defendant, who the attorney knows will testify falsely (under oath) insists on taking the stand against the attorney’s advice, the attorney is required by the Ethics rules to inform the judge in advance of the testimony.
The client’s plea of guilty/not guilty at arraignment is NOT testimony under oath and the attorney has no obligation, in fact would be prohibited, to informing the arraignment judge that the accused is lying.
An arraignment is not the trial and the person on the bench setting bail or denying it is not the trier of fact in the criminal case.
Even if the defendant’s attorney knows the defendant has committed the crime, the attorney is obligated to provide the best defense possible for the client without violating the rules of ethics or suborning perjury. This generally means that all rules have been followed by the prosecution, evidence presented is proper and that all experts are qualified and their testimony cannot not be broken for accuracy. This can not only make a difference as to the outcome of the trial, but appeals, length of sentence, amounts of fines, etc.
Ever since Gideon v. Wainwright every criminal defendant in America is entitled to legal counsel. Hopefully this will not be destroyed by the new administration and his appointee(s) to the Supreme Court. I am not hopeful that this protection will last.