A 42-year-old security guard who tried to behead his fiancee and gouged out her eyes believing she was possessed was yesterday sentenced to 10 years in jail.

The gruesome killing of 24-year-old administrative officer Elsie Lie Lek Chee nearly five years ago shocked the country. Yesterday, the horrific details of what happened in the couple's Jurong West rented room, as flatmates heard groans and wails through the night, were revealed in court.

Gabriel Lee Haw Ling, who pleaded guilty to a charge of culpable homicide, tried to decapitate Ms Lie using a variety of implements, including pruning shears, scissors, a rotary can opener and a hammer - just days after proposing to her. He also tried to amputate her right foot.

Originally accused of murder, Lee's charge was reduced after a psychiatric report found he had a brief psychotic disorder at the time of the killing, which was described by prosecutors as "cruel and unusual".

The couple met on a social networking site in April 2011. Two months later, they were living together even as Lee was divorcing his wife, a lawyer with whom he has two children.

He began to believe that the room they were renting in Jurong West Street 65 was haunted, and that Ms Lie was possessed. He took her to a Catholic church for an exorcism and made her carry a Bible in a waist pouch. When her colleague asked her about the Bible, Ms Lie replied that she was possessed.

He proposed to her during a trip to Genting Highlands in March 2012. On March 30, at 6pm, the couple went into the kitchen toilet of their home. They were inside for three hours. A domestic helper from the flat upstairs said she heard a male voice shouting: "Go back! Go back to the sky!" The couple's flatmates said Ms Lie looked pale and was supported by Lee when they emerged from the toilet.

The main tenant called the police at 11.10pm when loud groaning noises were heard from the couple's room. When two police officers arrived, Lee told them they had been quarrelling. Ms Lie, who was lying on a mattress on the floor where there were clothes strewn about, assured the police that she was just weak from a recent abortion.

The officers left at 11.45pm after telling the couple to keep it down. But the flatmates continued to hear groaning, wailing, whining and shouting from Lee.

At 6.40am, the police were called again after a flatmate noticed blood on the couple's room door. A paramedic who was first to the scene saw a topless Ms Lie covered in blood, lying face-up on top of a naked Lee. As the paramedic waited for the police to arrive - as he had assessed that the situation was unsafe - Lee gouged out Ms Lie's eyes and threw them out the window.

When the officers came, Lee was kneeling next to the body, groaning and chanting while holding a yellow object that resembled a cross.

A few bent metal spoons and a fork were found entwined in Ms Lie's hair. Various tools were found beside her, as well as a slice of her windpipe. Her eyeballs and clumps of hair were recovered at the foot of the block. An autopsy found multiple injuries to her head, neck and limbs, including a gaping 12cm wound across her neck. Her ankle had been cut to the bone.

Deputy Public Prosecutor Hay Hung Chun sought a term of at least 12 years, saying that Lee had "brutally and prematurely extinguished" his fiancee's life.

Lee's lawyer Sunil Sudheesan asked for a 10-year jail term, arguing that his client's psychiatric condition was in remission. He added that Lee came from a "strong Catholic background" and has believed in ghosts and spiritual possession since he was a child.

"He killed a lady that he loved, that is punishment for him emotionally... this is a heartbroken man who deserves one chance," said the lawyer. Lee's older brother, a surgeon, has promised to supervise him after his release.