(NewsNation) — Tara Martinez, a forensic scientist with Idaho State Police, took the stand Thursday in the Lori Vallow murder trial and said that fingerprints of Alex Cox, Vallow’s brother, were found in a plastic bag containing JJ Vallow’s remains, East Idaho News reported.

Vallow, 49, has pleaded not guilty to murder, conspiracy and grand theft charges in the deaths of her two youngest kids and her husband Chad Daybell’s previous wife Tammy Daybell.

“This is the most data that we’ve received. For a long time, many of us had suspected that Alex did in fact have something to do, at least, with the hiding of these bodies. Whether or not he was actually the perpetrator, no one will ever know,” Forensics expert Joseph Scott Morgan said during an appearance Thursday on “Elizabeth Vargas Reports.” “The fact that there was a latent print left behind by him, puts him in contact, with this bag, with the tape.”

FBI forensic examiner Douglas Halepaska, who also took the stand Thursday, said JJ’s sister, 16-year-old Tylee Ryan’s, bones had signs of stabbing and chopping injuries. While he was not able to determine what exact tools were used, the examiner speculated it was a blade tool such as a machete, hatchet or cleaver.

“It almost seems as if her (Tylee) remains in total had been burned, and then they went back, perhaps. It’s almost like they tried to dismember her body after it had been on fire,” Morgan speculated.

Tammy Daybell’s sister Samantha Gwilliam also testified and said that her sister was “perfectly healthy” during a visit together before she died, East Idaho News reported.

“Samantha says Tammy never indicated that she thought Chad was having an affair. In 2019, “something seemed off with them when they stayed with us and Chad wouldn’t converse with my husband,” the report states.

NewsNation legal contributor Sara Azari, who also weighed in on “Elizabeth Vargas Reports,” pointed out that when the defense puts on their case, they’re going to try and offer a different account of what happened.

“Ultimately, it’s going to be up to the jury to decide which set of experts are more reliable, which set of science is more reliable. … The investigation, and the analysis, the forensics here is extraordinary. … The question really becomes, we don’t know if it’s a male or female that stabbed or chopped Tylee. The problem is that doesn’t really even matter at the end when she (Lori) has a conspiracy charge, and there’s all these ties between Alex, Chad and her,” Azari said.

The official cause of death for JJ is asphyxia from a plastic bag being put over his head and duct tape over his mouth; Tylee was declared a victim of “homicide by unspecified means,” Ada County Coroner Dr. Garth Warren said Wednesday. JJ and Tylee went missing in September 2019. Their bodies were later found in Daybell’s backyard.

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