Lori Vallow murder trial: Cause of death for J.J. Vallow, Tylee Ryan revealed

A forensic pathologist testified on Week 4 of the Lori Vallow murder trial about how J.J. Vallow and Tylee Ryan died.

The so-called "Doomsday mom" is accused of killing her two youngest kids, ages 7 and 16. Their bodies were found buried on Chad Daybell's property.

Authorities determined that 7-year-old J.J. died of asphyxia with a plastic bag over his head.

J.J.'s mouth and ankles were reportedly bound with duct tape, and bruising was found on his arms and neck that occurred before he died. 

The coroner also said the manner of Tylee Ryan's death was a homicide, but the cause of death remains unknown. The teen's remains were found severely decomposed and had been badly burned.

The prosecution had called more than 30 witnesses, but Wednesday is the first time that a cause of death was revealed for the children.

FBI special agent Steve Daniels also returned to the stand Wednesday to detail the discoveries of the kids' bodies in Chad Daybell's backyard.

Another nugget of information from Dr. Warren – he says he found a drug called Gamma-hydroxybutyrate in JJ’s system. According to the DEA, it can be abused for euphoric and calming effects.

Dr. Warren said that based on the "inconclusive" amounts found in JJ, he couldn’t say whether the GHB was given to him or if it naturally occurred in his body.

Those who testified on April 26 include FBI special agent Steve Daniels, Dr. Garth Warren, Ada Co. Coroner, and chief forensic pathologist, and FBI forensic anthropologist Angi Christensen.

Lori's sister testifies

On April 25, Lori's sister Summer Shiflet testified against Vallow. 

She claims she played an active role in the loves of her niece and nephew JJ and Tylee, and said she was unable to get in touch with Vallow for months after the kids were reported missing.

The jury also heard a dramatic phone call between Shiflet and Vallow not long after their bodies were found buried in Daybell's backyard in Idaho.

"I think you were dancing on the beach, having a great time! Getting married! You took pictures and your kids don't deserve burials but you need to get wedding pictures? You don't think that's upsetting? And nobody knows except you and the Lord?" said Shiflet in the call.

"Yeah, ask Him," Lori responds.

For all previous and extensive coverage on this case, visit https://fox10phoenix.com/vallow + watch the in-depth special here.