Criminal defense law consists of the legal protections afforded to people who have been accused of committing a crime. Law enforcement agencies and government prosecutors have extensive resources at their disposal. Without adequate protections for the accused, the balance of power within the justice system would become skewed in favor of the government. As it is, fair treatment for criminal defendants often depends as much upon the skill of their defense attorney as it does the substantive protections contained in the law.
Defense attorneys know how to use constitutional guarantees to the advantage of their clients. For example, all criminal prosecutions are based upon evidence gathered by the government. This may include physical items of evidence, witness statements, confessions, drug and alcohol tests, and so fourth. The Fourth Amendment to the U.S. Constitution (applicable to the states through the 14th Amendment) prohibits the police from using unreasonable searches and seizures to gather evidence. If they do, a defense attorney will ask the court to suppress that evidence so it cannot be used at trial.
The Constitution provides many more protections that apply to the field of criminal defense law. Someone who has been tried and acquitted of a crime cannot again be charged with that offense, as mandated by the "double jeopardy" provision of the Fifth Amendment. The Sixth Amendment guarantees criminal defendants the right to a public trial, and in many cases, the right to have their guilt or innocence decided by a jury. It also affords the right to confront adverse witnesses, and to use the court's subpoena power to compel the appearance of favorable witnesses.
