World's Most Dangerous Prisoners

Fellow inmates consider James "Porky" O'Rourke to be one of the most dangerous and violent convicts in the UK prison system. At the age of 22, he killed a man by dropping a slab of concrete on his head.

Mother of two Joanne Dennehy launched a knife attack on a man she had lured back to her flat before stabbing two men out walking their dogs. Now locked behind bars, Dennehy is one of only three women currently serving a whole life order in the UK.

Mark Hobson is a man with an extreme propensity for violence, a notorious British spree killer who bludgeoned to death his girlfriend then seven days later sexually assaulted and killed her twin sister.

Covered in tattoos, his terrifying appearance adds to Jaime Osuna being one of the most feared men in the US prison system. Awaiting trial, he began practising Satanism and attempted to kill a fellow inmate.