That's a complicated question.
Typically these devices sit silent until there's an electrical problem. Thank God we don't have short circuits and overloads that frequently. When those conditions occur, these devices are expected to function as they were designed and clear the fault. When these devices are tampered with, the probability of them not operating correctly is many times greater. If the fault meets the device, then we have a potential catastrophe—fire and potential loss of life.
Who is responsible? Everyone. Typically, when there's a catastrophe everyone ends up in front of the judge. The results of a fire don't leave much evidence. That's why we hire an army of lawyers to help protect us.