It was meant to be the ultimate symbol of menace: carving '666' into his forehead. But in a phenomenal case of idiocy, convicted murderer Nikko Jenkins used a mirror - so the numbers came out backwards. The symbol is described in the biblical book of Revelation as 'the sign of the beast', and has since been popularized by the horror movie The Omen. However, with a series of upside-down 9s, Jenkins has fashioned himself an entirely unique - and irreversible - engraving. Botched: Nikko Jenkins (pictured in 2014) recently tried to carve '666' into his forehead but did it backwards . According to Omaha.com, Jenkins told his attorney about the incident in a phone call from his cell in Omaha, Nebraska. It comes amid the 28-year-old's ongoing appeal that he is mentally unstable and therefore ineligible to face the death penalty. Jenkins was jailed exactly one year ago for shooting dead four people in 10 days after being released from prison. During his murder trial in Douglas County, Jenkins was assessed by a doctor who concluded that he was 'a psychopath' and 'one of the most dangerous people' he had ever encountered. 'Psychopath': The 28-year-old, who a doctor described as 'one of the most dangerous people' he had ever encountered, may use the botched case of self-mutilation as evidence he is mentally unstable . Jenkins pleaded not guilty, then guilty, then ineligible for trial on the grounds of insanity. However, a judge dismissed the appeals and he was sentenced to life. The decision of whether he would be sentenced to death was delayed after Jenkins revealed he had carved a swastika into his skin. Following months of delays, he will face a panel in July to decide his fate. It is believed Jenkins may use his latest botched case of self-mutilation as further evidence that he is mentally unstable.
Nikko Jenkins, 28, was trying to etch the Revelation sign of the beast .
But he now has a series of upside-down 9s across his face .
It is believed he may use the botched case as evidence he is mentally unstable and therefore ineligible to face the death penalty .
Jenkins was convicted of shooting dead four people in 10 days after he was released from prison in Omaha, Nebraska, in 2013 .