Defendant Megan Huntsman, 39, is accused of killing the babies between 1996 and 2006, before Utah law was changed in 2007 to make murder a capital offense if a victim was younger than 14, Utah County Attorney Jeff Buhman said outside court after a hearing in the case.
Until the law was passed, killing a child was not considered one of the aggravating factors that can make someone eligible for the death penalty, he said.
Such factors also include the victim being a police officer, the killing occurring while another crime, such as rape, was committed, or if the defendant has already been convicted of another murder. Killing more than one person also is considered a capital offense but only if they die in the same incident.
Authorities say Huntsman was the mother of the babies and they were awaiting DNA testing to confirm that along with the sex of the children. Their causes of death also remain uncertain.
No labs in Utah can analyze the type of DNA that has been taken from the small corpses, so the FBI has been brought in to help, police said.
The bodies of the infants were found on April 12 in boxes in Huntsman's garage in Pleasant Grove. A seventh infant found in the garage is believed to have been stillborn.
During her brief court appearance, Huntsman mostly kept her eyes focused on the ground as she was informed of the charges. Her wrists were shackled to her waist, and she was wearing baggy, orange jail pants and a green shirt.
Defense attorney Doug Thompson told reporters after court that he has spoken with Huntsman but did not want to provide details on her state of mind.
"She seems fine but I don't really want to get into any of that," he said.
Prosecutors filed six first-degree murder charges against Huntsman. Each carries a possible sentence of five years to life. She has not yet entered a plea.
Buhman said a medical examiner has completed autopsies on the babies.
"We basically have an initial report so we have some information but not a lot yet," Buhman said, declining to provide further information.
Buhman said investigators will have to rely on reports from the medical examiner and a forensic anthropologist, along with Huntsman's statements to police, to determine the cause of death.
Huntsman's estranged husband, Darren West, discovered one of the infant corpses in the garage. Police responded and found seven tiny bodies in cardboard boxes.
Police said Huntsman acknowledged that from 1996 to 2006, she strangled or suffocated six of the babies, put them in plastic bags and packed them inside boxes in the garage south of Salt Lake City.
Pleasant Grove Police Detective Dan Beckstrom said police were working to corroborate Huntsman's story.
Investigators believe West is the father of the babies. He lived with Huntsman during the decade the babies were killed and was in federal prison on drug charges from 2006 until January.
Buhman said West is not a suspect.
"He's been very cooperative. We've had at-length discussions with Mr. West," Buhman said.
Authorities have said they think they know Huntsman's motive but declined to reveal it.
Huntsman was being held on $6 million bail and is due back in court on May 19, when her attorneys can decide if they want to request an evidence hearing.