BOISE — An FBI agent who specializes in analyzing cellphone records testified Monday in the Chad Daybell murder trial about phone locations that helped in his investigation.

Nickolas Ballance said after the bodies of 7-year-old Joshua "JJ" Vallow and his sister 16-year-old Tylee Ryan were located in Chad Daybell's backyard, he analyzed devices near where the bodies were found shortly after the children were seen for the last time.

He used cell towers the phones were connecting with to determine where the phones were.

Investigation into Tylee's death

Tylee Ryan was last photographed Sept. 8, 2019, during a family trip to Yellowstone. After this date, friends of Lori Vallow Daybell told the court they thought the teen was living at and attending BYU-Idaho, but someone from BYU-Idaho testified the school never received an application for her.

This information, introduced previously in Chad Daybell's trial, led investigators to believe Tylee had been killed on Sept. 9, 2019, so Ballance said he looked specifically at phone locations on that day.

A cellphone associated with Lori Daybell's brother and uncle of the children, Alex Cox, was at her Rexburg apartment that day between 2:42 a.m. and 3:47 a.m. and then back at his apartment in the same complex at 4:37 a.m.

At about 9:15 a.m., the agent said Cox's location was just south of Chad Daybell's home in Salem, Idaho. The two children were found buried in that backyard months later.

Ballance said the phone was in a spot "very similar" to where Tylee's body was found between 9:15 a.m. and 10:57 a.m. He pointed out one time where Cox's phone was near a gate that allows vehicles to enter the property. He said his report showing the location of Cox's phone behind the home was within a margin of error of between 3 and 8 meters.

About 11:45 a.m., Cox's location moved away from Chad Daybell's property. At that same time, Chad Daybell's phone made a call from near his home to Lori Daybell's phone, which was near her home.

He specified he was only getting a record of where a phone was at a specific time. "I'm not locating a person, I'm locating a device," Ballance said.

The FBI agent also talked about communications between Chad and Lori Daybell, telling jurors the two communicated "pretty regularly." On the morning of Sept. 9, 2019, there were multiple texts between the two starting at 7:20 a.m., and one phone call made by Lori Daybell, whose location is near her home at the time, to Chad Daybell at 8:03 a.m. They talked for just over two minutes.

Using locations from when Chad Daybell's phone received, texts, Ballance was able to determine he was at his residence around 9:30 a.m. that day, as well.

After noon, the phones of both Chad Daybell and Cox were around the homes of Lori Daybell and Cox.

Investigation into JJ's death

The last photo of JJ was taken on Sept. 22, 2019, and friends staying with Lori Daybell said they saw the boy that day but he was not there the next morning. Ballance said he was asked to look into the locations of Chad Daybell, Lori Daybell and Alex Cox.

Starting at 3:59 a.m. on Sept. 23, 2019, Chad Daybell sent multiple texts to Lori Daybell and received one in return.

Ballance said Cox was at his Rexburg apartment that morning from 9:01 a.m. to 9:41 a.m. Chad Daybell at 9:25 a.m. made a phone call from his home to Cox that lasted less than a minute. Afterward Cox's phone moved to Chad Daybell's property and was there between 9:55 a.m. and 10:12 a.m. He was back at his Rexburg apartment around 10:20 a.m.

At 10:13 a.m. that day, Cox made a phone call to Lori Daybell.

The agent said some of his locations were very close to the place where JJ's body was found.

During this same time period, Chad Daybell communicated with Lori Daybell multiple times again from his property between 9:30 a.m. and 10:27 a.m., according to Ballance.

Inconsistent story

Hannah Parker, whose mom is a cousin of Tammy Daybell, said she went to the viewing before Daybell's funeral and heard different stories from Chad Daybell about his wife's death in close succession. Once when she went through the line with her father and again when she went through with her mother.

Neither story was consistent with what Chad Daybell told a police officer and a coroner who responded to his wife's death.

When Chad Daybell was speaking to her father, Parker testified that he told them Tammy Daybell vomited around 10 p.m. that night and decided to go to bed and then he found her passed out and cold when he went to bed at 1 a.m.

In the conversation with her mother, she said Chad Daybell told them he went to bed with his wife because she had been coughing all day and was worried about her, then he woke up at midnight to her falling off of the bed.

When Parker's mother testified on Monday, she did not remember being told a specific time that Chad Daybell learned his wife had died, but said her falling off the bed woke Chad Daybell up and that is when he realized she had died.

Parker said she noticed the inconsistency and was confused. She also said he was not acting like someone whose wife had just died.

"I would have expected someone who had just lost their partner to be a little more distraught. And he was calmer than I would have expected him to be," Parker said.

The mother, Patricia Later, was emotional as she spoke about her relationship with Tammy Daybell. She said they grew up together and were like sisters. When she heard of Daybell's death, she said it made no sense to her.

"She was so young and healthy," Later said.

She said Chad Daybell would cry when others did, but mostly was just visiting — she felt like he "should have been more sad."

Later also said during the funeral service he said some things she felt weren't nice about his wife. She said he brought up that she had depression in front of a large group, and said that she wasn't easy to live with and was lazy.

When his children spoke at the funeral about helping their mother hide things from their dad — like her bringing home pets or her playing video games, she watched Chad Daybell's reactions. She said he initially looked concerned, but then would laugh off the comments.

Chad Daybell is charged with first-degree murder in the deaths of his wife and of JJ and Tylee. He is also charged with conspiracy to commit first-degree murder of each of the victims, grand theft and two counts of insurance fraud.

Lori Daybell was found guilty of murdering her children and conspiring to murder Tammy Daybell following a jury trial last year. She now faces two counts of conspiracy to commit murder in Arizona in relation to the death of her fourth husband, Charles Vallow, and in an attempt on the life of her former nephew-in-law, Brandon Boudreaux.

The jury trial will not be held on Tuesday because of staffing schedules at the Boise courthouse, but testimony is expected to resume Wednesday morning. KSL.com will begin streaming the trial on Wednesday at 8:30 a.m. MDT.

Friday's testimony:

'Something wasn't sitting well': Funeral director expressed concerns about Tammy Daybell's death

Jurors heard testimony from friends of the Daybell family on Friday during the trial for Chad Daybell, who is accused of murdering his wife and his future wife's two children.

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