People often suggest that attorneys who represent the guilty are in some ways immoral. It is suggested that if you are guilty you do not deserve a legal defense. Part of this mentality stems from society's belief that the Constitution protects only the innocent and that procedural protections exist only to exonerate the innocent who are unjustly accused.
The structure of our justice system is about preserving the right to a presumption of innocence. In order to preserve this inalienable right, we must afford a good legal defense to all who are accused, including those who are, in fact, guilty. Someone has to rise to the occasion, someone has to provide the service. The criminal defense attorney provides this service to even the most heinous offenders.
Defending the guilty is an act of redemption for the lawyer as well as the client. For the attorney, it is about defending the Constitution. You cannot pick and choose which parts of the Constitution you want to defend. Defense attorneys are called upon to defend child killers, gang members, and drug lords. They defend these individuals because this is the system of justice afforded to all by the United States Constitution.
Without the structure of the justice system, we would live in complete disorder, we would live under mob rule and vigilantism. Defense attorneys bring Order to the Law & Order. Defense attorneys do what the average citizen is often times incapable of doing, and that is seeing the accused as a person. Seeing the accused as our brothers, mothers, children. Defense attorneys see the accused as "innocent" and simply challenge the State to prove guilt. After all, the State prosecutors must prove "beyond a reasonable doubt" that the person accused is, in fact, guilty of the crime for which they are charged.
Consider this, not everyone that is killed is murdered and not everyone who kills is a murderer. To murder someone, there must be an absolute intent to kill. Sometimes, people are killed without any such intent. A defense attorney is a person who will help distinguish the set of events (ie. self-defense). A defense attorney will bring the proper charges to light (i.e manslaughter). A defense attorney will defend against improper charges and false accusations.
Providing a defense is not the same as defending the guilt of an individual. It is about defending the rights of an individual. It is about protecting the rights of every individual and defending the Constitution.