The Zong massacre was the mass murder of 133 African slaves by the crew of the slave ship Zong in the days following 29 November 1781. The Gregson slave-trading syndicate, based in Liverpool, owned the ship and sailed her in the Atlantic slave trade. As was common business practice, they had taken out insurance on the lives of the slaves as cargo. When the ship ran low on potable water following navigational mistakes, the crew threw slaves overboard into the sea to drown, partly in order to ensure the survival of the rest of the ship’s passengers, and in part to cash in on the insurance on the slaves, thus not losing money on the slaves who would have died from the lack of drinking water.
After the slave ship reached port at Black River, Jamaica, Zong’s owners made a claim to their insurers for the loss of the slaves. When the insurers refused to pay, the resulting court cases held that in some circumstances, the deliberate killing of slaves was legal and that insurers could be required to pay for the slaves’ deaths. The judge, Lord Chief Justice, the Earl of Mansfield, ruled against the syndicate owners in this case, due to new evidence being introduced suggesting the captain and crew were at fault.