Mohammed Tauseef Mumtaz, 25, had to be carried out of the dock by his father after being jailed for a minimum of 13 years for the murder of Naila Mumtaz, who was smothered at her Birmingham home in 2009.

The killer's brother-in-law, Hammad Hassan, was also imprisoned for at least 13 years, while his mother and father, Salma Aslam and Zia Ul-Haq, were both given minimum terms of 15 years by a judge at Birmingham Crown Court.

Mumtaz, his parents, both aged 51, and Hassan, 24, had denied both murder and manslaughter but were convicted of the more serious charge following a 12-week trial which ended in July this year.

The trial heard evidence that Naila, 21, was killed during attempts to render her unconscious as family members attempted to drive out a harmful "jinn" spirit.

Jurors also heard that Mumtaz, whose wife was six months pregnant, told police that she had tried to strangle herself at their home in Craythorne Avenue, Handsworth Wood, after becoming "possessed" by the spirit.

Passing sentence on the four defendants, Mr Justice Keith accepted that they had not intended to kill Naila, who moved to the UK in 2008 after an arranged marriage in Pakistan.

Although the jury's guilty verdicts were consistent with a finding that the victim was deliberately smothered by one or more of the defendants as others held her down, the judge said the panel's findings did not explain why she was attacked.

During his sentencing remarks, Mr Justice Keith said: "The four of you have been convicted of the murder of Naila Mumtaz - she was only 21 years old at the time of her death and had her life ahead of her.

"She was her parents' only daughter and her death has left a terrible gap in their lives.

"What aggravates the case is that Naila was pregnant at the time of her death, isolated from her family in a country unfamiliar to her, and spoke little if any English."

Possible motives for the offence raised during the trial were that the defendants believed Naila's unborn child was not her husband's - or that she was possessed by a jinn sent from Pakistan.

The judge, who ruled that it was unlikely the defendants believed Naila was pregnant by another man, said: "The other possibility explored in the course of the trial about why Naila was smothered was that the defendants believed that Naila had been possessed by a jinn, which had been sent from Pakistan by Naila's parents, and that they ... smothered her in order to get rid of the jinn.

"I regard this as a less unlikely explanation for what happened."

The judge urged the prison authorities to house Mumtaz, who suffers from a severe disability, in the same cell as his father so he can be properly supported during his imprisonment.

Naila and all four defendants were living at the same house in Craythorne Avenue when paramedics were called to the property in the early hours of July 8, 2009.

Ambulance staff did all they could to save the "ashen" and injured victim, who was found lying on a bed, but she was pronounced dead in hospital.

Jurors were told that numerous telephone calls were made to Naila's relatives in Pakistan, the emergency services and other individuals in the hours before she was taken to hospital.

During the calls, it was alleged that Ul-Haq claimed that a spirit had been sent from Pakistan, while a female at the house was allegedly heard to say "don't call an ambulance yet - we will cure her ourselves".

In his account to police, Mumtaz maintained that injuries to his wife's body were self-inflicted and claimed that a person was present at the house praying "to get the spirit out of her".

Before the life sentences were imposed, defence counsel urged the judge to accept that "genuine and sincere" efforts were made by the family to revive Mrs Mumtaz.

David Crigman QC, representing Aslam, said she lost her life in "unfathomable" circumstances, leaving her family by marriage entirely destroyed.

After Mrs Mumtaz's killers were jailed, Detective Inspector Simon Astle, of West Midlands Police, said: "This was a tragic and deeply upsetting case, where a young woman had her life so horrifically ended by those she loved and trusted.

"Naila was a pretty, outgoing young woman who was soon to become a mother for the first time.

"It is unthinkable that those who she was closest to would take her life in the belief that she had been possessed by evil spirits."

The officer went on: "Naila should now be enjoying the joys of motherhood and family life but instead her family back in Pakistan continue to mourn her death, still shocked and unbelieving that the family she entered into caused her death."

In a statement issued by West Midlands Police, Mrs Mumtaz's relatives described her as a "happy, confident and beautiful" young woman.

The family statement read: "She came to Britain to be with her husband; we entrusted our most treasured, beloved only daughter to him and his family.

"Naila was almost six months pregnant with her unborn son when she was killed in her home destroying her hopes, dreams and opportunities for the future.

"We are very grateful for the jury using plain common sense in bringing the perpetrators to justice.

"Naila will always be in our hearts and prayers and we hope her memory will live on by bringing about awareness of the issues surrounding her unfortunate death."