The court heard Danby and O'Toole jumped on Luke's head until it popped "like a marshmallow" then hid the 18-year-old's body under a mattress in a stream in May last year.
Danby spent the following day bragging how the young father's brains spurted all over his jeans and that the killing had promoted him into the 'A-Team' of crime.
He planned to slice off Luke's fingers and pull out his teeth to prevent his body being identified.
But he was arrested on the journey to the body with a pair of pliers and three kitchen knives after Hall could stand the violence no longer and called the police.
One police officer said: "There is only one word you can use to describe James Danby - psychopath."
The killers, who were living with Luke at a council house in Crow Lane, Romford, tried to blame each other for the killing and O'Toole said Danby was a "monster" who had destroyed all their lives. [...]
Luke, who was 5ft 7ins tall and weighed just seven stone, was one of a family of six children and had an eight-month-old son.
He had been living with his son and his mother but in the weeks before he had been arguing with his girlfriend and had asked to be rehoused by the council.
On the night he died he moved to the room at the council bungalow at Crow Lane, where Danby and the others lived.
The house had been divided into seven bedsit rooms with five on the ground floor and two more in the loft.
Behind the house were two more buildings not controlled by the council.
By chance an 18-year-old girl visiting the house that evening saw Luke and claimed he had raped her two years before.
Her complaint had been dropped after she was interviewed by police, who found her accusation was untrue.
But when the girl repeated her claims, Hall vowed to kill him.
The victim insisted he was innocent but police believe Danby may have been just looking for an excuse to kill someone.
Danby had never had a job and had only been in trouble for low level crime before the killing.
He was convicted of robbery when he went through the belongings of a man asleep on a bus and attacked him when he woke up.
Danby took a photograph of him on his mobile and showed it to the girl to confirm it was the man she claimed had raped her before he launched his ferocious, two-hour assault.
Luke was repeatedly punched in the face in his bedroom and in a shower room, spraying blood over the walls and floor.
The girl told the court: "His nose was bent and there was blood everywhere. It was awful."
He was so badly beaten that Hall said he looked like 'The Elephant Man' as he was bundled into her blue Fiat Punto.
Luke was repeatedly elbowed in the face by Danby on a journey to playing fields in Broadmead Road, Woodford Green.
Hall was driving and O'Toole was also in the car as Danby held a knife to the teenager's neck and said he was going to "slit his throat."
Luke was "finished off" on the bank of the stream with repeated stamps and kicks.
Hall told jurors she waited in the car while Danby and O'Toole took Luke down a path out of view.
According to O'Toole, Danby suddenly tried to strangle Luke by putting him in a "sleeper hold" before repeatedly stamping on his head.
O'Toole said he was so shocked by the attack he vomited near a fence.
'It's something a monster would do,' he told the court.
When Danby returned to the car he had blood spattered all over his jeans, top and hands and confessed to Hall: "I killed him, treacle."
They went back to Crow Lane and Hall then drove Danby, O'Toole and Duggan to Hou Hatch in South Weald where Luke's belongings and Danby's clothes were doused with petrol and burnt.
The following day when Hall announced she had killed a spider with her shoe, Danby replied: "Oi, you f***ing murderer, you're just like me."
Danby then insisted on Hall, O'Toole and another flatmate Billy Duggan going back to see the body.
Danby rolled the body into the stream and put the mattress on top of it.
Back at the house the group mopped and scoured Luke's bloodstains from the house as attempts were made to "remove all trace of him."
But Hall tipped off the police on the evening of May 28 after Danby announced he was going to return to the body for a second time remove the hands and teeth.
"He was laughing and joking about cutting Luke's head off," Duggan recalled.
Hall said she had been so sickened by the violence and Danby's horrific boasts she had to shop Danby.
Officers lay in wait at the stream and arrested the group as they returned with the knives and a pair of wire cutters.
It was claimed that Hall had initially attacked Luke after hearing about the rape claim.
O'Toole and Roberts were said to have joined in the attack.
But they all insisted they took no part in the violence and had to help Danby afterwards believing otherwise they would be killed next.
The convicted defendants are due to be sentenced on April 24.