A vegan couple is on trial for murder after their 18-month-old son starved to death.

On Wednesday, three months after the toddler's death, Ryan O'Leary, 30, and his wife Sheila, 35, were indicted on first-degree murder charges. Originally charged with manslaughter, the couple is set to appear in court on December 23.

If convicted, they could be executed.

To discover more about the case, check out the report below:

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Prosecutor Amira Fox accused the couple of "horrendous" abuse for feeding their child a diet of raw fruit and vegetables. A diet that resulted in the boy weighing just 17 pounds at the time of his death, as per the Metro.

To put this into context, a healthy seven-month-old baby should weigh 17 pounds - not an 18-month-old toddler.

Fox accused the O'Learys of torturing their son and their three surviving children, aged three, five and 11.

The toddler, whose name is not known, died from "starvation and extreme lack of care."

A vegan couple accused of murdering their child. [[imagecaption|| Credit: NBC6]]

Sheila O'Leary revealed to investigators that the family has a raw vegan diet, but that the boy was breastfed, and in the week leading up to his death, had only consumed breast milk.

The day before the toddler died, he experienced shallow breathing while being nursed by his mother. According to reports, she admitted that she should have called for help, but instead fell asleep with her husband.

An autopsy after the September 27 death revealed that the child had perished as a result of malnutrition, including dehydration, microsteatosis of liver and swelling of hands, feet, and legs.

Vegan parents who are charged with murder. [[imagecaption|| Credit: Fox4]]

When Sheila discovered that her son wasn't breathing, she called 911. While waiting for assistance, her husband attempted to revive the child, but it was to no avail and he was pronounced dead by paramedics.

Two of the couple's surviving children, aged three and five, were discovered with signs of malnutrition, discoloured skin and blackened teeth, and they have since been taken into the care of social services.

The eldest daughter was in the best health. Investigators discovered that this was because Ryan O'Leary was her stepdad and she frequently made visits to her biological father in Virginia. He is now caring for her full-time.

Vegan couple on trial for murder after 18-month-old starves to death