The related concepts of crime and law have a long history from which a variety of legal systems and legal forms have arisen that require the existence of lawyers. Lawyers are a highly trained professional class concerned with the study and practice of law, and a criminal defense attorney deals with law related to crime.
Specifically, a criminal defense attorney defends those who have been charged with a criminal offense. A criminal defense attorney prepares a case in an attempt to protect his clients’ civil liberties and get them found not guilty. Instead, a criminal defense attorney will try to keep the sentence as light as possible.
The legitimacy of law, in political theory, extends from some kind of governing body. The state, both as a theoretical construct and as an actual governing body, has historically often been the force behind the legitimacy of systems of law. In Western political philosophy, it has been argued that a state must be established to protect humans from one another. The role of the criminal lawyer is to act as a mediator in disputes involving damages or other criminal acts.
From Western political thought emerged the concept of the nation-state, which combines nationalist sentiments of patriotism with the form of the state. The revolutions of 1848 across Europe played a role in the rise of nationalism, as well as the liberal democracy and judicial systems we see in Europe and North America today.
Through this process of nationalism, each nation developed its own particular legal systems that share a common ancestor, but exhibit a wide range of variation that is largely dependent on the culture from which they derive. However, in cultures that allow people to defend themselves in criminal court, an attorney is absolutely necessary.
The presentation of documents and verbal discussions had to be coordinated in a hierarchical way, since the legitimacy of the law comes from the top in the chain of command. He made necessary the existence of courts and judges. Courts serve as official meeting places for lawyers, as well as opportunities for judges to decide cases. Some cases are decided by judges, but most criminal cases are decided by juries, to whom the criminal defense attorney must convince his client that he is innocent.
In modern legal systems, lawyers are still under the authority of judges, who in turn must answer to the state; however, lawyers also have a more important role, because people can defend themselves in court. In criminal cases, a defendant can defend himself with legal representation. In criminal court, a lawyer may try or defend individuals or groups in the interpretation and application of the laws. Court decisions set precedents that increase the likelihood that future court cases will be determined the same way.
As you can see, this profession has a long history and could not have reached its current form without the technology of writing and the accumulation of laws in its written form.