(NewsNation) — The official cause of death for JJ Vallow is asphyxia from a plastic bag being put over his head and duct tape over his mouth, while his sister, Tylee Ryan’s, is homicide by unspecified means, Ada County Coroner Dr. Garth Warren said Wednesday.

Homicide by unspecified means is a term used when a forensic pathologist examines a case and determines it was a homicide, but can’t pinpoint exactly what caused it.

Warren was giving testimony as part of the trial for Lori Vallow, the Idaho woman accused of killing her two children, JJ, 7, and almost 17-year-old Tylee. Vallow is also charged in connection to the death of her husband, Chad Daybell’s, previous wife. JJ and Tylee went missing in September 2019. Their bodies were later found in Daybell’s backyard.

“Each layer just got worse and worse. This poor child (JJ Vallow) fought for his life until the end; we learned that today. It’s just heartbreaking on a whole other level than the heartbreak we’ve all felt covering this case for three plus years, Gigi McKelvey, host of the “Pretty Lies & Alibis” podcast, said Wednesday during an appearance “Elizabeth Vargas Reports.”

On Wednesday, Warren testified that he performed JJ’s autopsy in June 2020. It took approximately four hours.

Warren said JJ was bound with duct tape, and had bruising on his arms and abrasions to his neck. Warren said these injuries to the neck are considered a red flag. The ones on his neck, Warren said, could be from JJ trying to get the bag off his head. Bruises on his arms likely happened before the child died, Warren added.

JJ was wearing a red pajama top and bottom with black socks when he died. At the time of the autopsy, his body had been in a state of decomposition.

As far as evidence gathered, the pajama tops, bottoms and socks were all submitted to law enforcement. According to the East Idaho News, low levels of ethanol (alcohol), a drug called GHB, caffeine and theobromine were found in a sample of JJ’s liver sent for a toxicology.

GHB, per the East Idaho News, can be found in tissues including livers after death. It is also another name for a prescription medication approved by the FDA to improve sleepiness and muscle weakness with narcolepsy. GHB can be misused as well as a “date rape” drug.

Warren said “there’s really no way” for him to tell for sure whether the GBH in JJ’s system was natural or if the drug had been given to him.

“I can’t say one way or another based on the levels,” he said, per the East Idaho News.

The process for Tylee’s autopsy differed from JJ’s since there wasn’t an entire body to examine, Warren testified. Her remains were received in three separate sealed bags, two body bags and one brown paper bag.

Warren was able to find Tylee’s organs, although unlike JJ’s autopsy where the organs were intact, his sisters were decomposed and had significant burns. In her toxicology report, ibuprofen, carboxyhemoglobin and iron were found in Tylee’s system. Carboxyhemoglobin is often released during a fire.

“If that is breathed in and the person is alive, you’ll get a high carboxyhemoglobin level. That’s why we did the test. In this particular case, the carboxyhemoglobin level came back extremely low,” Warren said, per the East Idaho News. “There is no evidence to support that Tylee was alive when she was burned.”

During court, photographs were shown from the autopsy to the jury and legal teams but not to the gallery, as Judge Steven Boyce decided it was inappropriate for them to be publicly demonstrated. Family members of the victims will be allowed to see the photos, if they wish to.

However, Larry Woodcock, JJ’s grandfather, told NewsNation on Tuesday that he doesn’t think it’s productive to see them. Instead, he said, he is seeking justice.

“It’s very hard for these jurors. These are people who don’t choose to look at this stuff for their everyday life jobs. So now their civic duty is to look at some of the worst things they could ever see, which is a child who was tortured and murdered. It showed on their faces today,” McKelvey told “Elizabeth Vargas Reports.”

This story is developing. Refresh for updates.