In a preliminary hearing held Monday, Dea Millerberg testified that she picked up 16-year-old Rasmussen on September 10 to babysit the couple's young children.
Millerberg detailed how no babysitting happened on that night, and how Alexis used methamphetamine and heroin with Eric.
Prosecutors have alleged that Alexis stopped breathing and died, either late at night on September 10 or early in the morning of September 11.
Eric Millerberg was charged with causing Rasmussen's death, along with unlawful sex with a minor, obstruction of justice and desecration of a human body.
Dea Millerberg is charged with desecration of a human body for her role in disposing of Alexis's corpse.
Dea testified in court on Monday against her husband, although it was unknown as to whether she had cut a deal with prosecutors in exchange for her testimony.
During her testimony, Dea Millerberg described the couple's relationship to the North Ogden teen, and what happened leading up to the night Alexis died.
Dea said she often paid Alexis in drugs for her babysitting services. She also testified that their relationship became more intense leading up to the girl's death.
Speaking of the night Alexis died, Millerberg said "Eric and I were planning to go shopping for our daughter's birthday. We needed a sitter, so I texted Lexi."
Millerberg described how Eric injected Alexis with drugs; one in the arm and another in the neck. Dea also testified that Eric and Alexis performed oral sex on each other, and that she was not involved in that sexual encounter.
Millerberg said that a short time later, Alexis started "freaking out" and demanded to be left alone while taking a hot bath in the couple's master bathroom.
It was 45 minutes later that Eric and Dea checked up on Alexis, who was standing in their bathroom, still "freaking out" and demanding to to be left alone.
Dea testified that she wrapped Alexis in blanket and left her on the bed in the adjacent bedroom.
When they went to check on Alexis about 45 minutes later, Dea testified, "She wasn't breathing. She had mucousy stuff coming out of the right side of her mouth."
Millerberg told the court that she was a trained nurse whose license had just expired, so she tried to revive Alexis by doing chest compressions and clearing her mouth of the fluids.
Dea said she soon realized that the girl was dead.
"It really was a panic," said Millerberg. "The idea of it was, we will lose our kids and go to jail, and there was nothing we could do to bring her back."
Millerberg also testified that she and Eric decided to not call authorities.
"We would put her body somewhere," said Millerberg.
Dea testified that she and Eric put Alexis' body in a box, which was placed in the trunk of their car.
Miller told the court that she and Eric took their toddler with them in the car as they drove around looking for a place to dispose of the body. Dea also testified that they left their 6-year-old child alone at home while they went to dispose of the body in the early morning hours of September 11.
After they found a spot just off the highway in Morgan County, testified that they backed the car into a secluded spot where Eric removed Alexis' body from the box in the trunk and dragged her into the brush and covered her.
Millerberg testified that they then drove to a site to dispose of the box, another site to dispose of the carpet that lined the car's trunk, and a car wash to clean the trunk out.
State Assistant Medical Examiner Dr. Joseph White also testified during the hearing.
White spoke of the forensic evidence gathered during the investigation.
"The circumstances are suspicious," said White. "The fact that the body was discovered so far away and she couldn't get there herself; It seemed suspicious, and that someone else was involved."
"It is highly unlikely this was an accidental death," said White. "The presence of drugs is a strong possibility as cause of death."
"Drugs are dangerous and unpredictable. Every time you use drugs there is a chance of death," added White.
White also testified that large amounts of meth and heroin were in Alexis' system, although her body was too decomposed to do a complete autopsy. Medical examiners have previously determined that the cause of Rasmussen's death was more than likely a drug overdose.
Dea filed for divorce from Eric after their arrests in connection with the Rasmussen death. Dea remained free on bail during Monday's court proceedings. Eric attended the hearing, although he remained in the custody of the Utah State Prison for parole violations on convictions unrelated to the Rasmussen case.
Prosecutors said that Eric's fellow gang members led investigators to the location in Morgan County where Alexis' body was dumped. Her remains were located on October 18.
A North Ogden police investigator told the court that after the Millerbergs disposed of Alexis' body, they drove to three different locations to get rid of evidence, including the Riverdale car wash.
Eric Smith testified that he helped Millerberg move Alexis' body on the night of September 12 or early on the morning of the 13th.
Smith offered his testimony on an agreement of immunity.
Smith testified that he had known Millerberg as "Rooster" since Spring 2011, and that they had the same gang affiliation.
Smith testified that he and Millerberg "kicked it a lot," "hung out," and "got high."
Smith said that Eric Millerberg contacted him late on September 12 or 13, leaving a message saying, "Bro, I need your help."
Smith testified that he went over to Millerberg's house, where Eric explained that a girl had overdosed.
Smithe said Eric said he might need some help to move her. Smith agreed, and the two of them got into a truck a drove to get some plastic gloves, a shovel and a plastic tarp.
Smith said the two of them went up a canyon to the location where Alexis' body was.
Smith said he and Eric moved her body deeper into the bushes.
Smith testified that he was later contacted by police, who offered not to charge him for moving body if he helped them locate Alexis' remains.
Following testimony during the hearing, the judge ruled that there was enough evidence to bind Millerberg over for trial.
Eric Millerberg then proceeded to pleading not guilty to all the charges against him.
Next court appearance for Eric will be May 15.
Millerberg's attorney told ABC 4 that Eric does not want to take a plea deal, because he feels he was not responsible for Alexis' death.
Weber County Attorney Dee Smith also told ABC 4 that everything Dea testified on Monday cannot be used against her in future court proceedings because of a deal that grants her immunity.
Stay tuned to ABC 4 News and ABC4.com for more on this story.