How typical of slave ship captains was Captain John Kimber? Some of his crew accused him of murder, but others described him as kind. On his first voyage, on the Recovery for James Rogers in 1791, he was accused by the surgeon of killing an enslaved girl by flogging her as punishment. He said she died of disease. The Abolition movement used it to show the inhumanity of the slave trade, whilst his employer, sailors and others testified that he was kind, generous and humane.

Ships' captains in general were known for hardness. There are many stories of cruel treatment, to crew and slaves alike, and few of humane captains.

The captain of the ship was the vital link in the slaving triangle, delegated to buy and sell on behalf of the merchants. He was responsible to the ship's owners for the outcomes of the voyage: in absolute charge of the ship, the crew, the stores, the trade goods, and responsible for buying enslaved Africans from the African traders and for their care during the transatlantic crossing of the Middle Passage. The care of the slaves was not from humanity, but for the sake of profit. The treatment of all aboard depended on his character. The historical evidence suggests that cruelty and abuse often went unpunished.

Part of his job was to make and maintain partnerships with African merchants, though captains often cheated and even enslaved the traders or their men, or forced trade at their price.