The rare books collection of the Law Library of Congress contains a copy of the trial of Aaron Burr for treason, a three volume set that was printed in Washington DC by Prescott and Company from 1807-1808. Aaron Burr was a prominent New York politician and the Vice President of the United States during the first term of the Jefferson administration. Today, Burr is best known for killing his political rival, Alexander Hamilton, in a duel in 1804 in Weehawken, New Jersey over a dispute about comments Hamilton made that disparaged Burr’s character. Following the duel, with his public career in shambles in the East, Burr looked to the West to regain his political fortunes. Allegations about the scope of Burr’s plan vary widely. Some accused Burr of attempting to separate the western states and territories from the United States in order to create a new western confederacy with himself at its head. Some said he was trying to conquer Spanish possessions in Mexico and South America where he hoped to declare himself Emperor. Some even accused him of plotting to depose President Jefferson. It is a fact that Burr sought, but failed, to obtain financial and military assistance for his plan from the United Kingdom through a contact with British Foreign Minister Anthony Merry; British Prime Minister Fox, however, did not support the effort. Whatever his precise objectives were, Burr also embarked on a tour of the west in 1805, meeting with prominent men and potential recruits. He began, but was unable to complete, a second tour of the west in 1806. During his first expedition, Burr met Harman Blennerhassett, a wealthy attorney who lived in a mansion on an island in the Ohio River, in what is today Parkersburg, West Virginia. Blennerhassett appears to have been the linchpin in Burr’s plan, providing Burr with funding and an island on which to drill troops and amass supplies. Burr had also enlisted as a co-conspirator the Senior Officer of the U.S. Army, General James Wilkinson. This alliance, however, turned out poorly for Burr’s scheme. As events progressed, Wilkinson became concerned that Burr’s plan would most likely fail. In order to save his own skin, he delivered dire warnings to President Jefferson about Burr’s character and intentions. Wilkinson subsequently sent evidence in the form of a ciphered letter to Jefferson. Wilkinson claimed the letter indicated that Burr commanded an army of seven-thousand men, which he intended to float down the Mississippi River on barges in order to seize New Orleans. Without naming Burr, President Jefferson responded with a presidential proclamation on November 27, 1806 warning citizens against participating in the expedition, which caused many of Burr’s recruits to flee. General Wilkinson continued the process of covering up his involvement in the conspiracy by presenting himself to Jefferson and Louisiana’s Territorial Governor as a savior of the republic. He arrested several of Burr’s associates in New Orleans, who he sent to Washington with a military escort. In response to a petition for a writ of habeaus corpus by these men, Chief Justice Marshall inquired into the legality of the men’s detention in an opinion titled Ex parte Bollman and Swartwout. In the opinion, Marshall recognized that a person could be guilty of treason as part of a general conspiracy even if they did not directly take up arms against the United States if they performed a part, even a remote part, and war was actually levied against the United States by other participants in the conspiracy. This is sometimes referred to as constructive treason. The Jefferson administration understood that the constitution would require the prosecution to prove that Burr had committed an overt act to levy war against the United States in order to obtain a conviction. It pinned its hopes on the description of an altercation one of Blennerhasset’s laborers claimed took place at Blennerhasset’s Island on December 10, 1806. The laborer claimed Blennerhasset’s troops drew their muskets in a confrontation with the state militia. Burr was not present on the island at the time, so the United States would have to draw upon the Ex Parte Bollman and Swartwout opinion, pointing to this altercation as an overt act of war in which Burr, even though not present at the time on the island, played a part in the furtherance of the general conspiracy. Burr was arrested by U.S. army Captain Edmund P. Gaines, commander of Fort Stoddert, near the town of McIntosh in what is now Alabama. He was then taken to Richmond for a hearing before the U.S. Circuit Court for Virginia. The court included Chief Justice Marshall who was there riding circuit as part of his duties as a Justice of the Supreme Court. Marshall expressed doubt that the actions that the allegations against Burr described amounted to levying war against the United States. He focused instead on the claim that Burr sought to invade Spanish lands in the West, and jailed him with a bond for a possible violation of the Neutrality Act of 1794, which made it a misdemeanor to wage war against a foreign power with which the United States was at peace. Burr posted a bond and returned in May of 1807 to face a grand jury. Selecting a jury was difficult, because the case was politically charged. Jefferson contributed to the tension by sending a message to Congress that declared Burr’s guilt was “beyond question.” Burr’s attorneys attempted to subpoena Jefferson to appear and turn over the letters he had received from General Wilkinson, along with his replies and subsequent orders. This provoked a brief separation of powers controversy, but ultimately while Jefferson did not appear personally, he turned over papers, claiming to have done so voluntarily. This, however, was almost certainly in order to avoid acknowledging the validity of the subpoena, and to preserve the ability to claim executive privilege in response to future subpoenas. To complicate matters for the prosecution, General Wilkinson doctored the cipher letter hoping to decrease even further the appearance of his involvement. Burr and Blennerhasset were indicted by the grand jury for treason and a misdemeanor for carrying on war with Spain. The prosecution argued that the altercation between Burr’s troops and the state militia that took place on December 10, 1806 was an overt act of war against that United States, and that Burr’s role in drafting, organizing and outfitting those troops supported a finding of constructive treason even though Burr was not on the island. The prosecution tried at first to introduce evidence of treasonous intent. Marshall, however, granted a defense motion to exclude much of that evidence, because it did not demonstrate the overt act of war against the United States that was required for a conviction. Marshall also found that the grand jury indictment was defective, because it did not make it clear that Burr was not on the island at the time, and that his alleged overt act of treason was limited to procuring the armed men. Marshall also noted that the prosecution could not offer the testimony of two witnesses that were required to prove an overt act of war. The testimony of the only witness they presented was also problematic: while the prosecution presented a laborer who claimed to have seen an altercation between Blennerhasset’s men and the militia, prosecution was unable to call the general in charge of the militia. In fact, the general had given an earlier deposition that contradicted the laborer’s claims. The court found Burr “not guilty by the evidence presented”, a qualification which irritated Burr. A little over a month later, he was also acquitted on the misdemeanor charge of waging war against Spain in violation of the Neutrality Act. The United States then argued for a motion to “commit” Burr for trial in a federal court in Ohio or Kentucky on treason and misdemeanor charges. Marshall ruled against the motion with regard to treason, but granted the motion to commit Burr to stand trial in Ohio for the misdemeanor of waging war against Spain. This time the government declined to prosecute him. The Burr trial is significant because of Marshall’s decision to narrowly construe the definition of treason found in Article III, Section III of the Constitution, holding that the mere advocacy of a treasonous design will not sustain a conviction. It also represents a remarkable moment in the history of this country when a former vice president was tried for as a serious charge as treason.