Josiah W. Gibbs, a professor of linguistics at Yale, was the man most responsible for bringing the African's own story of the Amistad incident to the American people. It was through the determined efforts of Gibbs that a Mendi translator was located.

Josiah Gibbs began his work by visiting the Africans in their New Haven cell. He held up a finger and said "one." He held up a single coin and said "one." Finally, Grabeau sensed what Gibbs was trying to do and shouted "eta," the Mendi word for one. Eventually, Gibbs began to build up a limited Mendi vocabulary, including words for the numbers one through ten. In the course of these efforts, Gibbs was also able to determine that at least three different African languages were represented in the group, although most were Mendi speakers.

Gibbs began a search for an English-speaking Mendi on the waterfronts of New Haven and New York. He would go up to blacks and begin counting from one to ten in Mendi, looking for signs of recognition. In New Haven, he found a sailor named John Ferry who knew some Mendi, but his vocabulary proved too limited to be of much use and Gibbs continued his search along the New York waterfront. James Covey, rescued from a slave boat by the British and trained by British missionaries in Sierra Leone, turned out to be the key to unlocking the Amistad Africans' story. Gibbs received permission from the captain of the H.M..S. Buzzard, the British warship which employed Covey, to take him to meet the Africans. Soon the captives began to spill out heir stories of their lives in Sierra Leone, their capture, their voyages, and their mutiny. Gibbs undertook an extensive interrogation of Cinque, who then asked Gibbs if he could arrange for them instruction in the English language. Gibbs replied that he would gladly do so.

In January of 1840, Gibbs testified at the district court trial in Hartford. He began with a detailed explanation of the importance of language to a determination of whether the Amistads were recently arrived from Africa, or had resided for years in Cuba, as their documents indicated. He pointed out how the name of each corresponded to a place, object, or thing in Mendi, and how if they had been in Cuba for years their names would have been "corrupted in form and sound." Gibbs testimony was finally cut off by Judge Judson who announced that he was "fully convinced that the men were from Africa, and it is idle to deny it."