-- Lt. Jackson (as played by Ji-Tu Cumbuka)
Film academics suggest that the true Blaxploitation efforts had pretty much died out by the mid-1970's. (Some of what I've seen online asserts that, by 1975, these pictures had lost any strength and/or clout at the box office.) Still, a few projects -- like Dr. Black, Mr. Hyde (occasionally cited as Dr. Black And Mr. Hyde) -- didn't see the light of day until 1976, so it might be best to see this as something released on the tail end of the dying movement. Given its timing -- and given the fact that the trend had already produced features like Blacula (1972), Blackenstein (1973), and Scream Blacula Scream (1973) -- I think it's still safe to assume that such an obvious reference to Robert Louis Stevenson's Dr. Jekyll And Mr. Hyde (which endured many theatrical and television incarnations up to this point) was meant to follow those same footsteps.
Interestingly enough, the film's IMDB.com page gives absolutely no credit to the Stevenson work as serving as inspiration for Dr. Black, as the script's attribution is assigned solely to Larry LeBron as screenwriter with Lawrence Woolner crafting its central ideas. While this film is LeBron's sole contribution to film, Woolner's biography shows him chiefly as a producer with a solid handful of genre entries to his name. Dr. Black was directed by William Crain, a name already established in the Blaxploitation effort as having brought the aforementioned Blacula to life on the silver screen. The film starred Bernie Casey, Rosalind Cash, Marie O'Henry, Ji-Tu Cumbuka, and Milt Kogan.
Here's the plot summary as provided by the good people at IMDB.com:
"An African-American scientist develops a formula to regenerate dying liver cells, but it has the unfortunate after-effect of turning him into an albino vampire with a mania for killing prostitutes. A tough police lieutenant investigating the murders discovers the existence of the dual-personality killer, and determines to bring him in."
As always, thanks for reading ... and live long and prosper!