There is no way for a criminal defense lawyer to know if the client is guilty. Clients very rarely admit to the full extent of their crimes. nnIf the lawyer does know that the client committed a crime, he is not permitted to assist in perjury. Perjury is when the lawyer allows the client to give false testimony while being in knowledge of the crime committed. nnBut this does not mean that the lawyer can’t defend their client. There are many grounds that can still be pleaded.