On the evening of March 5, 1770, a crowd of Bostonian citizens gathered and began taunting a British soldier.  Reinforcements under the command of Captain Thomas Preston arrived to support the soldier.  In the ensuing confrontation the British soldiers opened fire, killing five of the colonists.  This event became known in American history as "the Boston massacre."

The citizens of Boston were outraged by what they perceived to be outrageous conduct by the British soldiers and Captain Preston and his soldiers were indicted for murder.  The anti-British feeling was so high that no lawyer would defend the soldiers.  John Adams, a vocal critic of the British occupation and later President of the United States, recognizing a lawyer's duty to provide an adequate defense for even the most despised of defendants, came forward and represented the soldiers in the ensuing trial.  At the conclusion of the trial all but two of the soldiers were acquitted.  The two soldiers who were convicted were founds guilty of manslaughter, not murder.
Adams wrote in his diary, "The part I took in defense of Captain Preston and the soldiers, procured me anxiety, and obloquy enough. It was, however, one of the most gallant, generous, manly and disinterested actions of my whole life, and one of the best pieces of service I ever rendered my country. Judgment of death against those soldiers would have been as foul a stain upon this country as the executions of the Quakers or witches, anciently."
"the right to be heard"
Tennessee Constitution, Article 1, Sec. 9. Right of the accused in criminal prosecutions.
  "That in all criminal prosecutions, the accused hath the right to be heard by himself and his counsel; . . ."
  The right to be represented by counsel in a criminal prosecution is a fundamental right recognized in the 6th Amendment to the United States Constitution and in the Tennessee Constitution.
  Criminal defense lawyers are often asked, "How can you represent someone who is obviously guilty?"
  My quick lawyer answer is that guilty is a legal term.  All persons charged with a crime are presumed innocent.  That's the law.  A defendant is guilty only after he is found guilty by a court or jury, or pleads guilty.  Beyond that, however, the answer is really quite simple.  In a criminal case a lawyer has two roles.  One is that of an adviser to the defendant/client.  In that role, the lawyer informs the defendant as to the law applicable to the facts of the case.  He tells the client what options he may have in seeking to resolve the case.  The lawyer's second role is that of an advocate.  In that role the lawyer REPRESENTS the accused.  He speaks for and on behalf of the defendant.  He does for the accused what the accused would do for himself if he had the necessary skill and experience.  Imagine a judicial system in which the accused was not only denied a lawyer, but was prohibited from questioning his accuser, or even speaking on his own behalf.  Would anyone dare suggest that such a system was fair.  The government always has a lawyer to speak for it (the district attorney).  The government has trained professionals (policemen) to  investigate and gather evidence in a case.  When you think of that, could any system that denied the accused comparable assistance ever be deemed fair.
  Not everyone charged with a crime elects to plead not guilty and go to trial.  As a matter of fact, many people charged with crime enter guilty pleas.  The issue then is not guilty/not guilty, but what is the appropriate punishment.  As an example, with some exceptions, the sentence range for a Class A misdemeanor is from 0 to 11 months, 29 days imprisonment and a fine from $0 to $2500.  Should everyone receive exactly the same sentence?  If that is so, why have a range of punishment?  A judge must consider a number of factors in arriving at an appropriate sentence.  A defense attorney's role in the sentencing stage of the case is to assist the defendant in providing the court with information favorable to the defendant so that the judge may impose a fair sentence.
  The role of an attorney for the accused (all accused) in criminal cases is so vital to the fair functioning of our system of justice that it, like the jury itself, is constitutionally guaranteed.