The whole point of lawyer-client confidentiality is that
whatever is said between a lawyer and a client is secret. This is so that if a client reveals to a
lawyer that he is guilty, the lawyer doesn’t have to reveal this information to
anyone, even law enforcement. It is a
lawyer’s job to represent people, even if they are guilty.
Although it is morally questionable to represent clients they know are guilty, it is important that all individuals have access to a lawyer, and important that all lawyers are able to defend their clients to the fullest. If the lawyers don't know whether or not their clients committed the crimes, then they will be inadequately able to defend their clients. So, lawyers should represent clients they know are guilty, because it is necessary that they know whether or not their clients are guilty in order to proceed with the client's defense.