I think you're referring to the 6th amendment (excerpted below). Keep in mind this is the RIGHT of the accused, not a benefit for the government, so while I would love for him to have a speedy trial, the government does not have the right to unreasonably speed it up.

"In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining wit- nesses in his favor, and to have the Assistance of Counsel for his defence."