Handcuff
I watched him. The handcuff didn't't seem to bother him. It was a handcuff he had used to force a drugged man staying with him. He even drilled a hole in a young boy's head to make a zombie out of him.
Altogether it's not so strange if you think about what doctors did and still do to people. All those "expertise" is the result of experiments. Experiments on corpses, animals, disabled, crazy, poor and imprisoned people.
Was Jeffrey Dahmer crazy or was't he much different from Leonardo da Vinci who did some really crazy stuff too in the name of science, the nazis or Japanese?
What does s person, his brain need to get off the common path to experiment on others, innocent people and even start eating them. Dahmer might have been sick but if you look to his eyes it looks logical to me. Basic needs of a person that is still an abandoned, neglected child.
The escaped man with the strange handcuff finally made the police have a closer look at Jeffrey and his apartment. Jeffrey was never impolite, not loud which is a good reason why he wasn't investigated. He was't socializing.