Zoosadism is a type of Sadism in which it involves pleasure derived from cruelty to animals. It can also be a paraphilia, where people are sexually aroused by torturing animals. Zoosadism is part of the Macdonald triad, a set of three behaviors that have been considered a precursor to psychopathic behavior.

Some studies have suggested that individuals who are cruel to animals are more likely to be violent to humans. According to The New York Times:

The FBI has found that a history of cruelty to animals is one of the traits that regularly appear in its computer records of serial rapists and murderers, and the standard diagnostic and treatment manual for psychiatric and emotional disorders lists cruelty to animals as a diagnostic criterion for conduct disorders.

Helen Gavin wrote however in Criminological and Forensic Psychology (2013):

This is not a universal trait, though. Dennis Nilsen had difficulty initiating social contact with people, but loved his faithful companion, Bleep, a mongrel bitch. After his arrest, he was very concerned for her welfare, as she was taken to the police station too.

Alan R. Felthous reported in his paper "Aggression Against Cats, Dogs, and People" (1980):

A survey of psychiatric patients who had repeatedly tortured dogs and cats found all of them had high levels of aggression toward people as well, including one patient who had murdered a boy.

This is a commonly reported finding, and for this reason, cruelty to animals is often considered a warning sign of potential violence towards humans.