First of all, a criminal attorney is not representing someone they know is guilty--they're ensuring that a trial and the evidence presented against them is carried out in a fair and legal way and according to the U.S. Constitution. They are defending the Constitution and the system. Attorneys do not decide guilt, and they don't ask that question about guilt of their client. There are legal mitigating defenses to crimes and the evidence may not be sufficient to support a guilty verdict. Furthermore, It's the prosecution's job to present evidence and witnesses against the criminal defendant. If a guilty criminal is not adjudged accordingly, the prosecution is the one who didn't do its job. A jury according to the Constitution is to make that final decision and an attorney is supposed to be a voracious advocate for their client no matter the circumstances.
