Trivia: The same man that stops McQueen from popping out the eye of the first prostitute stops Abberline while he's kissing Mary Kelley (you can tell by the numbers on his uniform).
Trivia: While based on actual events and characters, "From Hell" takes considerable liberty with facts, in addition to leaving much of its convoluted fictional plot unexplained. The real Chief Inspector Frederick Abberline's first wife died of tuberculosis two months after they married (she was not pregnant at the time). Abberline remained married to his second wife for over 50 years, and they never had children. Abberline was not clairvoyant, was never an opium or absinthe user, either, and he died at the ripe old age of 86. The movie fabricated everything except a handful of essential historical facts regarding the Ripper murders.
Trivia: During the scene where Abberline is talking to the doctor in the classroom, if you listen to the dialogue the doctor confesses to being the killer. He doesn't come right out and say it. He tells Abberline that the killer is right-handed and uses his right had to illustrate and that he should be looking for someone with a knowledge of human anatomy. He does everything but say "I'm the killer."
Answer: In the original book, Merrick's appearance is used to show William Gull's education, expertise as an anatomist and that he recognises and respects cultural diversity - Gull assures Merrick that, had he been born in India, he would be worshipped as a descendant of the elephant-headed god, Ganesa. In this spirit, Gull even offers the victim of his first Ripper slaying to Ganesa as a sacrifice, as Indians make a sacrifice to Ganesa at the beginning of an important enterprise. Merrick is present as a vehicle to establish the rich nature of Gull's character. When it comes to the film, however, this subtlety is completely lost - it seems very much that the scriptwriter noted Merrick's appearance in the book and felt that it would be cool to include the character in his script. As such, as you point out, it does feel that Merrick's presence, stripped of the subtleties of the book, is almost entirely pointless.
Tailkinker ★