A violent and controlling boyfriend beat a vulnerable young woman to death in a jealous rage after she refused to tell him her Facebook password, a court has heard.

Kane Boyce, 34, of Beckenham, brutally punched, kicked and stamped on 20-year-old Paula Newman's head in a sustained attack after flinging her from his car onto a New Addington street, prosecutors alleged.

Miss Newman, who had learning difficulties, died of severe brain damage following the assault in Elmside, off Fieldway, in the early hours of November 12, 2013.

She had been in a seven-month relationship with Boyce, who a jury at the Old Bailey on Monday heard could be "sadistic and cruel" and had been "manipulative, controlling and the extremely violent" to previous partners.

In the weeks before Miss Newman's death he became "obsessed with getting access" to her Facebook account and had accused her of cheating on him, prosecutor Gillian Etherton told the court.

On the night of the alleged murder, a witness who lived in Elmside heard Boyce shouting "log on, log on" before telling Miss Newman, who was shrieking and crying, "if you don't log on we'll see what happens".

Ms Etherton told the jury: "This defendant is a man who is jealous, controlling and violent.

"The defendant in a violent rage beat and very likely kicked or stamped on Paula's head causing Paula severe and irreparable brain injury bringing about her death."

In the days before Miss Newman's death, the court heard Boyce told a friend she was a "lying cheating slag" and said: "I've asked for this Facebook account and she won't give it over to me for love nor money."

He is said to have snooped on his girlfriend even as paramedics fought to save her life at a friend's house in Dunsfold Way, New Addington, where he took her following the alleged attack.

Ms Etherton said: "'Evidence shows that her phone was used to access or attempt to access a number of sites between 4.59am and 6.20am, a time when we know she would have been incapacitated due to the severity of her injuries."

The court heard Boyce left the house while paramedics were battling to save Miss Newman and returned home to change his shoes, throwing away the pair wore while allegedly kicking to death his girlfriend.

The couple, who met living in their shared house in Aviemore Road, Beckenham, are said to have initially enjoyed a happy relationship but by the end of summer 2013 were regularly arguing.

Friends of Miss Newman said she "changed completely", with one, Stefani Taylor, telling police: "He [Boyce] had complete control of her and I had never seen her like that before.

"I pleaded with her to leave him but she would always say she loved him."

The court heard Boyce did not like Miss Newman going out, monitored her phone and would take it away from her as a punishment.

Six days before her death Boyce read a Facebook conversation between Miss Newman and an ex-boyfriend, with whom she had confided about her unhappiness.

Boyce saved a screenshot of the conversation and texted two friends offering them "a gram and a half for someone to fuck her shit up".

On the night of the attack, the couple's landlord heard Boyce screaming at Miss Newman, swearing and calling her names.

In the early hours of November 12, Boyce and Miss Newman arrived the house in Dunsfold Way. Miss Newman was incapable of walking alone, had been sick and was covered in mud.

Boyce's friend's daughter noticed Miss Newman's bra a strap was broken, her neck bore "finger-marks", her face was "swollen including her lips and nose, she had scratches on her face and she saw a bruise on her back which looked like a fist".

Boyce took Miss Newman to a friend's house in Dunsfold Way, New Addington, following the alleged attack

Miss Newman died the next day at Croydon University Hospital. Boyce gave several different accounts of what had happened, claiming Miss Newman had jumped out of a moving car.

But a post-mortem examination found extensive injuries that pathologist Olaf Biedrzycki concluded were the result of an assault rather than a fall.

Miss Newman's arms, face, jaw and neck bore bruising suggesting she had been forcefully gripped, her left cheek bore a pattern resembling the sole of a shoe and a blunt force had bruised her ear so severely it left a "tattoo impression" on her skull.

Boyce pleaded guilty to manslaughter in July last year, but denies murder.

He claims he pushed Miss Newman, causing her to stumble and bang her head against a wall, after she punched him.

But Ms Etherton said: "Kane Boyce alone was the aggressor that night. He was, the Crown suggests, driven by jealousy and anger about Paula's Facebook activity and on the day of her death he was aggressive and threatening about this activity.

"In the early hours of November 12 Paula received, not a single push causing her to fall, but a sustained beating at the hands and very likely foot of this defendant causing her severe head injury and resulting in her untimely death.

"Kane Boyce must have intended to cause Paula Newman really serious harm."

The trial continues.