In my dissertation, I examine how enslaved men and women engaged with disability and health status in their legal claims, during the transition from colonial reform to independence, in order to understand the centrality of these claims in Atlantic subjecthood, contests of authority, and freedom. Whether in petitions for freedom or invoked during prosecution in criminal trials, problems in a slave's physical or mental condition –known as defects –determined his or her value and contextualized how colonial officials interpreted and responded to slaves' behavior. Given the low credibility attributed to slaves' testimonies (when they could testify), medical practitioners were thought to provide a rational, empirical account of what happened, based on evaluation of the body. Importantly, medical theorizing influenced the court's reception of slaves' claims, and doctors acquired a new role as figures of expertise in the legal realm, often competing or collaborating with the established authority of lawyers and religious leaders. My research takes existing scholarship on slaves' legal strategies in new directions by attending to the ways that slaves' health status informed their arguments and outcomes, and to the role of medical practitioners in contradicting or legitimizing their claims. I suggest that including medical practitioners in legal matters created a new, strategic potential for slaves' claims, and increased opportunities for social mobility for doctors in the late eighteenth and early nineteenth centuries. I focus on two sites, Cartagena and Philadelphia, which were directly connected by the flour trade, important sites for the arrival and distribution of enslaved Africans, and which served as key entrepôts for the circulation of political and scientific ideas in the Atlantic world. My project delineates the ways that colonial law became inseparable from colonial medicine, and how slavery and colonialism shaped the origins of medical training in the Americas.