Prisoner wrote 666 backwards on his forehead because he forgot he was looking in a mirror

                        Nikko Jenkins – idiot or psychopath? (Picture: Douglas County)

A prisoner tried to write ‘666’ on his own forehead but forgot he was looking in the mirror so it came out as upside down ‘999’s.

It is believed convicted murderer Nikko Jenkins wrote the bungled ‘sign of the beast’ self-mutilation in a bid to avoid the death penalty.

The 28-year-old inmate is said to have told a judge during a recent telephone hearing of the irreversible mishap.

Jenkins reportedly told Judge Peter Bataillon that he carved the 666 because he is not receiving treatment for his purported mental illness.

He asked the judge to order the Nebraska State Patrol to investigate.

But the judge declined, reports local news site Omaha.com.

Jenkins is looking to avoid the death penalty (Picture: AP)

It is not clear yet whether Jenkins will use the latest self-mutilation to try to get himself again declared incompetent before he can face a death-penalty hearing.

Jenkins mutilated himself last year with a Charles Manson-style swastika on the forehead which resulted in a delay to the hearing.

It took a year before the judge declared him competent to stand trial and was just the latest antic in a case that has dragged on for 20 months.

Jenkins is scheduled to go before a three-judge panel in early July which will decide if he should be executed for his 2013 killing spree of four people.

The killer says he acts under the voice commands of a serpent god, but psychiatrists are split on whether is he a genuine schizophrenic.