A couple who caused the death of their three-year-old son by denying him adequate food and then buried his body in their garden are due to be sentenced.

Tai and Naiyahmi Yasharahyalah will appear in custody at Coventry Crown Court on Thursday, a week after they were found guilty of causing or allowing the death of a child, what was described as “breathtaking” neglect, and perverting the course of justice.

A two-month trial was told Abiyah Yasharahyalah, who was restricted to an “extreme” vegan diet, died in early 2020 from a respiratory illness with a more than minimal cause of his death being severe malnourishment which led to rickets, anaemia and stunted growth.

Finding the couple guilty on all charges, jurors accepted prosecutors’ claims that Abiyah was ill-treated by being denied adequate nutrition and medical care.

A post-mortem examination of Abiyah’s “skeletal” remains and other tests failed to identify how he died, but suggested he was also suffering from severe dental decay and six fractures to his right arm, legs and ribs, possibly caused by a fall about six weeks before his death.

London-born Tai, a medical genetics graduate who also used the first name Tai-Zamarai, and former shop worker Naiyahmi shunned mainstream society and left Abiyah’s body buried at their property in Handsworth, Birmingham, when they were evicted in March 2022.

They were eventually arrested in December 2022 while living in a caravan in Glastonbury, Somerset, having previously spent time living in a shipping container.

Jurors unanimously convicted both defendants after hearing how they kept the body of Abiyah in their bed for eight days, before embalming and burying the toddler in an 80cm-deep grave at the rear of their then-home in Clarence Road, Handsworth.

The trial was told that police visited the Clarence Road property three times: in February 2018 when Abiyah was alive; again in September 2021 after his death; and then in March 2022 to assist in the couple’s removal for non-payment of rent.

The trial was told that instead of contacting the NHS, the couple – who told police they had renounced British citizenship and had an “off-grid” existence – tried to treat their son’s final illness with garlic and ginger.

The pair, whose diet largely consisted of nuts, raisins and soya milk, were both “extremely thin” when they were arrested on December 9 2022, leading to the discovery of their son’s body five days later.

Tai and his 43-year-old wife, who was born in Birmingham, denied the charges against them, telling the court they did not act wilfully and believed Abiyah would recover from a flu-like condition.

Former fitness instructor Tai, aged 42, told police in interview that he had carried out an “eight-day ritual” hoping that Abiyah would “come back”, but had eventually decided to conduct a burial in accordance with his culture on what he regarded as sacred ground.

Both defendants said they were living in a “kingdom” set up by Tai, which involved an unsupplemented vegan diet and adherence to a “slick law” legal framework he had invented.

The court heard the defendants married in 2015 and changed their names from Donald Nnah and Donna Graham after forming what they viewed as their own religion.

Opening the case for the Crown at the start of the trial, prosecutor Jonas Hankin KC claimed the couple had jointly neglected Abiyah by failing to provide him with enough food or any medical help.

During his closing speech to jurors, Mr Hankin alleged it would have been obvious to both defendants that Abiyah, whose teeth would have been wobbly, was in considerable pain from abscesses and other ailments.

Referring to a comment made by Abiyah’s mother that “nature has a way of doing things”, Mr Hankin told the court: “That is their attitude, ‘we’re right and nature will decide’. It is breathtaking arrogance and cruelty.”

Malnutrition of the severity suffered by Abiyah was simply not seen in the UK, the barrister said, with the defendants having “for reasons best known to themselves” driven themselves and their son into conditions more commonly seen in the developing world.

Mr Justice Wall remanded the couple in custody last week, removing bail which had been granted during the course of the trial.