Aaron Burr Jr. (February 6, 1756 September 14, 1836) was an American politician and lawyer who served as the third vice president of the United States from 1801 to 1805. Burr's legacy is defined by his famous personal conflict with Alexander Hamilton that culminated in Burr killing Hamilton in a duel in 1804, while Burr was vice president.

Burr was born to a prominent family in New Jersey. After studying theology at Princeton, he began his career as a lawyer before joining the Continental Army as an officer in the American Revolutionary War in 1775. After leaving military service in 1779, Burr practiced law in New York City, where he became a leading politician and helped form the new Jeffersonian Democratic-Republican Party. As a New York Assemblyman in 1785, Burr supported a bill to end slavery, despite having owned slaves himself.At age 26, Burr married Theodosia Bartow Prevost, who died in 1794 after twelve years of marriage. They had one daughter, Theodosia.

In 1791, Burr was elected to the U.S. Senate, where he served until 1797. Burr would later run as the Democratic-Republican vice-presidential candidate in the 1800 election. An unintentional electoral college tie between Burr and presidential candidate Thomas Jefferson resulted in the House of Representatives voting in Jefferson's favor, with Burr becoming Jefferson's vice president due to receiving the second-highest share of the votes. Although Burr maintained that he supported Jefferson, the president was highly suspicious of Burr, who was relegated to the sidelines of the administration during his vice presidency and not re-nominated as Jefferson's running mate in 1804.

During his last year as vice president, Burr engaged in the duel in which he fatally shot Hamilton, his political rival, near where Hamilton's son Philip Hamilton died three years prior. Although dueling was illegal, Burr was never tried, and all charges against him were eventually dropped. Nevertheless, Hamilton's death ended Burr's political career.

Burr traveled west to the American frontier, seeking new economic and political opportunities. His secretive activities led to his 1807 arrest in Alabama on charges of treason. He was brought to trial more than once for what became known as the Burr conspiracy, an alleged plot to create an independent country led by Burr, but was acquitted each time. With large debts and few influential friends, Burr left the United States to live as an expatriate in Europe. He returned in 1812 and resumed practicing law in New York City. Burr's brief second marriage resulted in divorce and further scandal. Handicapped by a stroke and financially ruined, Burr died at a boarding house in 1836.

A grand jury is a jury—a group of citizens—empowered by law to conduct legal proceedings, investigate potential criminal conduct, and determine whether criminal charges should be brought. A grand jury may subpoena physical evidence or a person to testify. A grand jury is separate from the courts, which do not preside over its functioning.Originating in England during the Middle Ages, grand juries are only retained in two countries, the United States and Liberia. Other common law jurisdictions formerly employed them, and most others now employ a different procedure that does not involve a jury: a preliminary hearing. Grand juries perform both accusatory and investigatory functions. The investigatory functions of grand juries include obtaining and reviewing documents and other evidence, and hearing sworn testimonies of witnesses who appear before it; the accusatory function determines whether there is probable cause to believe that one or more persons committed a particular offense within the venue of a district court.

In Ireland, they also functioned as local government authorities. In Japan, the Law of July 12, 1948, created the Kensatsu Shinsakai (Prosecutorial Review Commission or PRC system), inspired by the American system.The grand jury is so named because traditionally it has more jurors than a trial jury, sometimes called a petit jury (from the French word petit meaning "small"). A grand jury in the United States is usually composed of 16 to 23 citizens, though in Virginia it has fewer members for regular or special grand juries.