Lawyers for Jeremy Bamber, who is serving life in prison for murdering his family in a gun massacre, have reportedly unearthed evidence to suggest his schizophrenic sister could have shot and killed herself.

Sheila Caffell, who was found dead next to her twin sons and adoptive parents in 1985, was the prime suspect for the case which is now the subject of new ITV drama White House Farm.

But suspicion of the model, also known as Bambi, was dropped after a judge ruled it 'inconceivable' of her to be able to take her own life after she was found with two gunshot wounds to the neck at intervals.

However, Bamber's lawyers have reportedly discovered statements by senior officers and the police surgeon that suggest Ms Caffell only had one bullet hole - meaning there could be a possibility she could have murdered her parents.

Lawyers for Jeremy Bamber, who is serving life in prison for murdering his family in a gun massacre, have reportedly unearthed evidence that suggest his schizophrenic sister could have shot and killed herself

They allege the documents were never seen by the trial jury - and have since asked ITV to postpone the drama after they believe the new evidence could prove Bamber's innocence, according to the Guardian.

During the trial in 1986, police and the coroner believed Caffell had killed herself because a rifle was found next to her body without a silencer attached.

But the silencer was later found in the gun cupboard in the house - which formed a significant part of Bamber's conviction. He was jailed for life at Chelmsford crown court in October 1986.

Judge Justice Drake told at the Chelmsford Crown Court trial it was 'inconceivable' that she could have unscrewed the silencer, put it in the cupboard and 'return upstairs to the bedroom before taking her life by two shots – one with some interval between the other?'.

Sheila Caffell, who was found dead next to her twin sons and adoptive parents in 1985, was the prime suspect for the case which is now the subject of new ITV drama White House Farm

In the ITV series, a pivotal moment is when police realise Caffell has been shot twice in the neck, with the investigating officer saying: 'Well it can't be bloody suicide then.'

Sheila 'Bambi' Caffell, was murdered in August 1985 along with her six-year-old twin sons and the couple who adopted her, Nevill and June Bamber. All five were shot in the family's remote Essex farmhouse by the Bambers' adopted son, Jeremy.

Police initially believed that Sheila, who suffered from schizophrenia, had committed the murders before killing herself.

However, weeks later, her adoptive brother Jeremy Bamber was arrested in connection with the crime and was convicted of the murders in October 1986.

The newly discovered evidence suggest that five senior officers and the police surgeon on the case had recorded only one wound shot on Caffell's neck.

Sheila 'Bambi' Caffell, who was murdered in August 1985 along with her six-year-old twin sons and the couple who adopted her, Nevill and June Bamber

According to the Guardian, Chief Superintendent Harris said in his witness statement that he had seen the gun resting below 'an entry wound beneath her chin.

Meanwhile, Chief Superintendent said he saw 'a younger female with a wound to her throat'.

Bamber's lawyers do not dispute that Caffell had two gunshot wounds - which was recorded by crime scene photographs at the scene.

But one theory is that the gun went off as police entered the scene, according to the publication.

Police had originally believed Bamber's story, and he managed to convince detectives that his sister Sheila had carried out the attack.

Bamber had called police to tell them there was something wrong at the Essex property, and that his sister had 'gone crazy and had the gun'.

The massacre of his family became known as the White House Farm murders after the name of his parents Essex farmhouse (pictured) where it took place in 1985

Prior to the funeral, senior officers had believed Bamber's story.

But one detective hadn't been convinced by Bamber and claimed he had informed senior officers that they 'had not been happy' with the way Bamber had carried himself at the funeral.

In the new ITV show, a disturbing portrayal shows the killer sobbing at the service for his slain parents and his sister and bears a striking similarity to film and photographs taken at the ceremony in August 1985.

The suspicions didn't go away and it was then that the teacher called detectives to tell them he believed Bamber had been acting.

Police initially believed that Sheila, who suffered from schizophrenia, had committed the murders before killing herself

Bamber, 59, (pictured in 1986) convicted of all five murders. Since then he has appealed against his life sentence several times

Detectives say it was these 'crocodile tears' that convinced them that he was acting and was responsible for murdering his family at the Essex farm house in Tolleshunt D'Arcy in August 1985.

He was then arrested and charged. A year later he was convicted of all five murders. Since then he has appealed against his life sentence several times.

He is a category A prisoner at HMP Wakefield in Yorkshire.

Bamber has slated Fox's portrayal of him in the new ITV drama, saying it was 'nothing like him'.

In the ITV drama, Bamber, played by Fox, breaks down in tears in front of the television cameras

He said: 'I am concerned ITV are now cashing in on the tragedy,' but ITV insisted it carried out 'meticulous research'.

Mark Newby, a solicitor advocate at Quality Solicitors Jordans, which represents Bamber, told the Guardian: 'The jury only heard of the two shots, which was relied upon by the crown to support their case, but this wasn't the whole picture.

'It represents yet another significant aspect to this case which supports Jeremy Bamber and undermines this conviction.'