The Mari are an advanced civilization whose entire populace is telepathic. The Mari have lived for centuries without crime, due in part to a law forbidding voilent thoughts. Anyone found in possession of violent thoughts is immediately arrested and placed through a 'rehabilitation' process by where the violent memory engrams are erased from the subjects mind.
Lieutenant B'Elanna Torres was arrested by the Mari constabulary following an incident where it was believed that Torres had incited an act of violence. The Mari people are particularly susceptable to violent acts following the introduction of a violent memory from an alien species, caused in part due to the lack dealing with violence over the past centuries. The preliminary investigation placed a brief violent memory of B'Elanna as the cause of the incident and she was subsequently detained for engram removal.
Further investigation by Lieutenant Commander Tuvok cleared Torres of the crime, when his investigation led to the discovery of a black market of violent memories. The merchant with whom the crew had been interacting during Voyager's stay at the planet was discovered to be a major contributor to the black market, using memories he gained by probing the minds of alien visitors.