Bad blood.

The Tuskegee Study was set up in Alabama in 1932 in order to find a more effective way of treating syphilis which was widespread throughout the state's scattered rural communities. Begun in good faith, it turned into a clandestine experiment on black people to discover the effects of untreated syphilis. The subjects were enticed into participating in the study by offers of free medicine; they were not told the truth about their condition, for which the 'medicine' was useless. The study continued even after penicillin became available as an effective treatment, and continued until exposed by the press in 1972.