From LawGuru Wiki
Arraignment is a common law term for the formal reading of a criminal complaint, in the presence of the defendant, to inform him of the charges against him. In response to arraignment, the accused is expected to enter a plea. Acceptable pleas vary from jurisdiction to jurisdiction, but they generally include "guilty", "not guilty", and the peremptory pleas (or pleas in bar), which set out reasons why a trial cannot proceed. In addition, US jurisdictions allow pleas of "nolo contendere" (no contest) and the "Alford plea" in some circumstances.
In the UK arraignment is the first of eleven stages in a criminal trial, and involves the clerk of the court reading out the indictment. The defendant is asked whether they plead guilty or not guilty to each individual charge.
 Guilty and Not Guilty pleas
If the defendant pleads guilty an evidentiary hearing usually follows. The court is not required to accept a guilty plea. During that hearing the judge will assess the offense, mitigating factors, and the defendant's character; and then pass sentence. If the defendant pleads not guilty, a date will be set for a preliminary hearing or trial.
 What if the defendant enters no plea?
In the past, a defendant who refused to plea (or, "stood mute") would be subjected to peine forte et dure. But today in all common law jurisdictions, defendants who refuse to enter a plea will have a plea of not guilty entered for them on their behalf.
 The Federal Rules of Criminal Procedure
The US Federal Rules of Criminal Procedure state: "...arraignment shall...[consist of an] open...reading [of] the indictment...to the defendant...and calling on him to plead thereto. He shall be given a copy of the indictment...before he is called upon to plead."