Perry Hall Juvenile Law Lawyer, Maryland

The earliest and most common test for criminal insanity, in which a criminal defendant is judged legally insane only if he could not distinguish right from wrong at the time he committed the crime. For example, a delusional psychotic who believed that his assaultive acts were in response to the will of God would not be criminally responsible for his acts.

Latin for a 'guilty act.' The actus reus is the act which, in combination with a certain mental state, such as intent or recklessness, constitutes a crime. For example, the crime of theft requires physically taking something (the actus reus) coupled with the intent to permanently deprive the owner of the object (the mental state, or mens rea).

One of the most sacred principles in the American criminal justice system, holding that a defendant is innocent until proven guilty. In other words, the prosecution must prove, beyond a reasonable doubt, each element of the crime charged.

The defendant's formal answer to criminal charges. Typically defendants enter one of the following pleas: guilty, not guilty or nolo contendere. A plea is usually entered when charges are formally brought (at arraignment).

Criminal Law Traffic TicketshomeGLOSSARY jury A group of people selected to apply the law, as stated by the judge, to the facts of a case and render a decision, called the verdict. Traditionally, an American jury was made up of 12 people who had to arrive at a unanimous decision. But today, in many states, juries in civil cases may be composed of as few as six members and non-unanimous verdicts may be permitted. (Most states still require 12-person, unanimous verdicts for criminal trials.) Tracing its history back over 1,000 years, the jury system was brought to England by William the Conqueror in 1066. The philosophy behind the jury system is that--especially in a criminal case--an accused's guilt or innocence should be judged by a group of people from her community ('a jury of her peers'). Recently, some courts have been experimenting with increasing the traditionally rather passive role of the jury by encouraging jurors to take notes and ask questions.

The burden of proof that the prosecution must carry in a criminal trial to obtain a guilty verdict. Reasonable doubt is sometimes explained as being convinced 'to a moral certainty.' The jury must be convinced that the defendant committed each element of the crime before returning a guilty verdict.

A quaint phrase that refers to the recording of an arrested person's name, age, address and reason for arrest when that person is brought to jail and placed behind bars. Nowadays, the book is likely to be a computer. Usually, a mug shot and fingerprints are taken, and the arrestee's clothing and personal effects are inventoried and stored.

A rule of evidence that disallows the use of illegally obtained evidence in criminal trials. For example, the exclusionary rule would prevent a prosecutor from introducing at trial evidence seized during an illegal search.