Assistance of Counsel Clause
Every defendant has the right to a lawyer without a conflict of interest.  Here is an example of a conflict of interest: a lawyer is defending two different people.  A client named Smith wants to blame his crime on another client named Jones.  A lawyer is supposed to do what is best for their clients.  Here, the lawyer cannot do that for both clients.  If the lawyer blames Smith's crime on Jones in court, he is hurting Jones.  If he does not blame the crime on Jones, he is refusing to defend Smith the way Smith wants.  This is not fair to either client.  Also, the lawyer cannot do the best possible job for both clients at the same time.