Preventive detention is used when the prisoner is deemed a danger to society and there is a great chance of his committing violent crimes in the future.
The preventive detention may be continued every two years until it is found the convict is unlikely to commit further crimes or be a menace to the public.
Preventive detention has a minimum non-parole period of five years in prison, but the sentencing judge can extend this if they believe that the prisoner's history warrants it.