A herbalist who told a 13-year-old diabetic boy's family to rub lavender oil into his spine instead of using insulin has been jailed in California after the boy died from complications relating to type-1 diabetes.

Timothy Morrow, 84, was sentenced on Monday for practicing medicine without a license, as well as one count of child abuse likely to produce great bodily injury or death, to which he entered a no contest plea.

Prosecutors told the court how Morrow, who founded the Common Sense Herbs company, first started "treating" Edgar Lopez after his mother went along to one of his talks, KTLA reports. Morrow advised the family to stop the boy using his diabetes medication shortly afterwards, telling them it was "poison". He advised they instead use herbs, including lavender, which he sells on his website.

Lopez became ill shortly after his family followed Morrow's advice. He was struggling to keep food down and lost a lot of weight, had difficulty breathing and felt cold to the touch. At this point the herbalist told the family their son was going through a "healing crisis" and advised them not to seek medical help, the Washington Post reports.

“He told us that if we took the child to the hospital, he would get killed there,” his father, Delfino Lopez Solis told the jury last week during the two-week trial. The next day the boy died at home.

"The medical examiner determined the victim would have lived had he received proper medical treatment,” said a statement from the US Attorney’s Office.

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The defense told the court that all the herbs "prescribed" by Morrow had the warning "this product is not intended to diagnose, treat, cure or prevent any disease" on the label, according to ABC News. However, the mother told the court that the herbalist had described his "pancreas reg" (pancreatic regeneration protein) as "God's insulin" and that it could be used instead of actual insulin.

The court was told that his mother, Madrigal, had been "brainwashed" by Morrow, who claims on his website that he cured his own cancer. Before her son's death, she refused to give Edgar his insulin even though he'd asked for it, believing Morrow when he told her it was poison.

"On my last call [to Morrow], my son was telling him, may I call 911, may I call 911?" ABC reports Madrigal told the jury. "My son could not breathe anymore."

Morrow told them no.

This may not be the only case in which Morrow advised people to stop receiving medical treatment. A widow of a cancer patient told the jury his wife, Carol Anne Waisanen, used herbal "treatment" instead of conventional medicine upon Morrow's advice, WFTV reports.

Morrow has been sentenced to four months in Los Angeles County Jail and ordered to pay $5,000 to the victim's family for funeral costs.