BOISE — Dr. Lily Marsden, who attended the exhumation and autopsy of Tammy Daybell, said Tuesday she believes someone else restricting Daybell's airway caused her to die.

Marsden also testified during the Chad Daybell murder trial that the bruises on his wife Tammy's arms and chest were "acute" and her "body had not started to mount a response to try to clean up the injury," meaning the bruises likely were caused in the hours before or minutes after her death.

Marsden and Dr. Erik Christensen, Utah's chief medical examiner at the time of the autopsy, concluded that Tammy Daybell died from asphyxia, and the manner of death was homicide.

Marsden testified that smothering — a bag over Daybell's head or weight on her chest — would not leave any outward signs of asphyxiation on the body for investigators to find. She said the bruises on Daybell's arms and chest could indicate that two other people were there when she was killed, or just one person.

Marsden said she and Christensen were not able to see anything that would have caused Daybell's death in their initial examination. She said they found pulmonary edema, which could be caused by heart failure, a drug overdose, drowning or asphyxia — when a person is prevented from breathing.

When an autopsy comes back negative, or with no apparent causes of death like this one, Marsden said the three things they consider are seizures, heart failure and asphyxia. She said Daybell's heart was normal and it would be very unusual for a woman of her age to begin having seizures without a visible medical cause, like a tumor.

"Asphyxia is a diagnosis of exclusion; and in our opinion, we did thoroughly exclude the other potential causes of death," Marsden said.

KSL.com is streaming the trial daily.

Chad Daybell is charged with first-degree murder in the death of his wife, as well as the deaths of 7-year-old Joshua "JJ" Vallow and 16-year-old Tylee Ryan, the children of his new wife Lori Vallow Daybell. He is also charged with conspiracy to commit first-degree murder of each of the victims, grand theft and two counts of insurance fraud.

Alex Cox's location history

On Monday, FBI agent Nickolas Ballance testified Alex Cox's cellphone data shows his phone had been at a church near Chad Daybell's home on two significant dates — the day when a man dressed in black pointed a gun and fired at Tammy Daybell and 10 days later, on the day Tammy Daybell died. Cox, who has since died, was Lori Daybell's brother.

Rick Wright, an FBI special investigator, testified Tuesday about other locations of Cox's phone, specifically around the times when JJ and Tylee disappeared.

He said on Sept. 8, 2019, Cox and Tylee were seen on cameras entering Yellowstone National Park; and while they were in the park, Cox's phone location indicates the only spot they stopped was at the public area around Old Faithful. Wright said initially they were concerned that something may have happened to Tylee while they were in the park because there are no reports of anyone seeing her after that point.

He said Cox's phone was near Chad Daybell's home in Salem, Idaho, where Tylee's remains were eventually found, on the morning of Sept. 9, 2019, between 9:21 a.m. and 10:57 a.m. Afterward, the location data shows Cox's phone traveling back to Rexburg and then stopping at a Del Taco.

On the morning of Sept. 23, 2019 — the first day JJ was absent from school — Cox's phone was also located behind Chad Daybell's home between 9:55 a.m. and 10 a.m.

Wright listed a few other times Cox's phone was at Chad Daybell's residence, each time for shorter periods. He also showed more specific locations for each of the dates on Chad Daybell's property, showing that Cox's location was near where each of the bodies were found on the dates investigators believe the children were killed.

He also testified about other phone locations he found notable, including multiple trips to a gun range.

Wright said Cox's phone was usually at his home overnight, but between Oct. 2 and Oct. 3, 2019, it was at Lori Daybell's apartment overnight. He said that lines up with when investigators believe Cox was in Arizona and tried to kill Brandon Boudreaux. He also said Cox's phone was at a Walmart on Sept. 25 when another phone was purchased.

Boudreaux testified that someone driving what looked like Tylee's Jeep fired shots at him outside his home.

Wright also said Cox's phone locations showed he may have parked in one of the few locations near the Daybell home where someone can pull off the road, outside of driveways, for a few minutes on the date Tammy Daybell reported someone had pointed and fired a gun or a paintball gun at her in her driveway.

On that day, Oct. 9, 2019, he said a phone they believe was purchased by Cox at Walmart sent 10 messages to Chad Daybell between 7:30 p.m. and 10:30 p.m.

His phone was also located at a church building near the Daybell residence around 10 p.m. on Oct. 18, 2019, the night Tammy Daybell died, before going to a hotel near Idaho Falls.

KSL.com is streaming the trial each day. Testimony is expected to resume Wednesday at 8:30 a.m. MDT.

Monday's testimony:

Tylee's best friend, investigators who examined her remains testify in Chad Daybell murder trial

Jurors in the Chad Daybell murder trial heard testimony Monday from victim Tylee Ryan's best friend and from investigators who testified about marks found on Tylee's bones.

Related topics