A crew drowned more than 130 captives to save water, then the owners billed the insurers

For three days, the men of the slave ship Zorg dragged living people to the rail and threw them into the Atlantic. They started with women and children, including one baby. By the end, more than 130 Africans had been drowned to save drinking water, as many as 140 by some counts, and their bones still lie on the seabed.

The ship was lost. The man in command, Robert Stubbs, had mistaken Jamaica for the neighboring island of Hispaniola, which was enemy territory during the American Revolutionary War, and sailed three days past his destination. Beating back against the wind would take 10 days, and the ship was completely out of water. The crew was down to 11 men, the captain was sick almost to madness, and about 70 Africans had already died of dysentery and scurvy.

What makes the killings historic is what happened next in London. The owner, Gregson, had insured the Africans at 30 pounds a head and demanded payment for the people his crew had killed. The standard contracts covered captives who died in an insurrection, but not those who died of natural causes or suicide, and they said nothing about people thrown overboard. When the insurers refused to pay, Gregson sued.

The case came before the Earl of Mansfield, the chief justice of the British Empire, at London's Guildhall. Stubbs was the only witness. He testified that the ship was out of water and the killings were necessary, meaning the crew had no choice or all would have died, and the merchants won. Mansfield summed up the logic in a line that became infamous: "The case of the slaves is the same as if horses had been thrown overboard."

But one person watching was troubled that no one spoke of murder. That watcher wrote an anonymous letter to London's largest newspaper asking why 130 people could be drowned with talk only of insurance money. Olaudah Equiano, a former enslaved man living in London who had bought his freedom, brought the letter to Granville Sharp, a self-taught London legal activist devoted to ending slavery.

Sharp persuaded the insurers to seek a retrial and paid to have the hearing transcribed in shorthand. This time the lawyers made what Siddharth Kara describes as a new argument in a Western court, that Black captives had the same claim to water and life as the white crew. Then Stubbs, pressed on the stand, admitted that it had rained in the middle of the killings.

The scandal freed no one on the Zorg, but it did something larger. News of the trial spread, and in 1787, 12 men met in a printing shop and pledged to abolish slavery, the start of what Kara calls the first abolition movement.