The historian Samuel Eliot Morison described it in 1969 as the most important court case involving slavery before being eclipsed by that of Dred Scott v. Sandford in 1857.

On July 2, 1839, one of the Africans, Joseph Cinqué, freed himself and the other captives using a file that had been found and kept by a woman who, like them, had been on the Tecora, the Portuguese ship that had transported them illegally as slaves from West Africa to Cuba.

[6] The crew deceived the Africans and steered La Amistad north along the East Coast of the United States, where the ship was sighted repeatedly.

[7] Taking them to the Long Island Sound port of New London, Connecticut, Lieutenant Gedney presented officials with a written claim for his property rights under international admiralty law for salvage of the vessel, the cargo, and the Africans.

[4] As the British had entered into a treaty with Spain prohibiting the slave trade north of the equator, they considered it a matter of international law for the United States to release the Africans.

The British applied diplomatic pressure to achieve that such as invoking the Treaty of Ghent with the US, which jointly enforced their respective prohibitions against the international slave trade.

While the legal battle continued, Dr. Richard Robert Madden, "who served on behalf of the British commission to suppress the African slave trade in Havana," arrived to testify.

[12] He made a deposition "that some twenty-five thousand slaves were brought into Cuba every year – with the wrongful compliance of, and personal profit by, Spanish officials.

[12][page needed] Madden, who later had an audience with Queen Victoria concerning the case, conferred with the British Minister in Washington, D.C., Henry Stephen Fox, who pressured U.S. Secretary of State John Forsyth on behalf "of her Majesty's Government.

It is under these circumstance that her Majesty's Government anxiously hope that the President of the United States will find himself empowered to take such measures, in behalf of the aforesaid Africans, as shall secure to them the possession of their liberty, to which, without doubt they are by law entitled.

[13] Secretary of State Forsyth requested from the Spanish minister, Chevalier de Argaiz, "a copy of the laws now in force in the island of Cuba relative to slavery.

"[13] The Spaniards maintained that even if it was believed that the Africans were being held as slaves in violation of "the celebrated treaty of humanity concluded between Spain and Great Britain in 1835," it would be a violation of "the laws of Spain; and the Spanish Government, being as scrupulous as any other in maintaining the strict observance of the prohibitions imposed on, or the liberties allowed to, its subjects by itself, will severely chastise those of them who fail in their duties.

The Spanish also sought to avoid talk about the law of nations, as some of their opponents argued that it included a duty by the U.S. to treat the Africans with the same deference as would be accorded any other foreign sailors.

[clarification needed] Specifically, they noted that A case before the circuit court in Hartford, Connecticut, was filed in September 1839, charging the Africans with mutiny and murder on La Amistad.

[citation needed] It was entered into the docket books of the federal court as United States v. Cinque, et al.[15] Various parties filed property claims with the district court to many of the African captives, to the ship, and to its cargo: Ruiz and Montez, Lieutenant Gedney, and Captain Henry Green (who had met the Africans while on shore on Long Island and claimed to have helped in their capture).

[citation needed] The abolitionist movement had formed the "Amistad Committee," headed by the New York City merchant Lewis Tappan, and had collected money to mount a defense of the Africans.

[17] The abolitionists' main argument before the district court was that a treaty between Britain and Spain in 1817 and a subsequent pronouncement by the Spanish government had outlawed the slave trade across the Atlantic.

[citation needed] Concerned about relations with Spain and his re-election prospects in the South, U.S. President Martin Van Buren, a Democrat, sided with the Spanish position.

He ordered the schooner USS Grampus to New Haven Harbor to return the Africans to Cuba immediately after a favorable decision, before any appeals could be decided.

[18] Contrary to Van Buren's plan, the district court, led by judge Andrew T. Judson, ruled in favor of the abolitionists and the Africans' position.

In January 1840, Judson ordered for the Africans to be returned to their homeland by the U.S. government, and for one third of La Amistad and its cargo to be given to Lieutenant Gedney as salvage property.

Introducing copies of correspondence between the Spanish government and the U.S. Secretary of State, he criticized President Martin Van Buren for his assumption of unconstitutional powers in the case:[21] This review of all the proceedings of the Executive I have made with utmost pain, because it was necessary to bring it fully before your Honors, to show that the course of that department had been dictated, throughout, not by justice but by sympathy – and a sympathy the most partial and injust.

124), which recognized "that possession on board of a vessel was evidence of property,"[22] Adams said that did not apply either since the precedent was established prior to the prohibition of the foreign slave trade by the United States.

Lt. Gedney and the USS Washington were to be awarded salvage from the vessel for having performed "a highly meritorious and useful service to the proprietors of the ship and cargo.

Upon the merits of the case, then, there does not seem to us to be any ground for doubt, that these negroes ought to be deemed free; and that the Spanish treaty interposes no obstacle to the just assertion of their rights. ...

Abolitionist supporters took the survivors – 36 men and boys and three girls – to Farmington, a village considered "Grand Central Station" on the Underground Railroad.

Former members of the Amistad Committee later founded the American Missionary Association, an integrated evangelical organization that continued to support both the Mendi mission and the abolitionist movement.

The revolt aboard La Amistad, the background of the slave trade and its subsequent trial is retold in a celebrated[32] poem by Robert Hayden entitled "Middle Passage", first published in 1962.

Howard Jones published Mutiny on the Amistad: The Saga of a Slave Revolt and Its Impact on American Abolition, Law, and Diplomacy in 1987.

African-American artist Hale Woodruff painted murals portraying events related to the revolt on La Amistad in 1938, for Talladega College in Alabama.