“Even the intelligent and educated layman has small and sometimes no skill in the science of law. If charged with crime, he is incapable, generally, of determining for himself whether the indictment is good or bad. He is unfamiliar with the rules of evidence. Left without the aid of counsel, he may be put on trial without a proper charge, and convicted upon incompetent evidence, or evidence irrelevant to the issue or otherwise inadmissible. He lacks both the skill and knowledge adequately to prepare his defense, even though he has a perfect one. He requires the guiding hand of counsel at every step in the proceedings against him. Without it, though he be not guilty, he faces the danger of conviction because he does not know how to establish his innocence”.

(Powell v. Alabama, 287 U.S. 45 1932)​