PROVO, Utah — A Utah mother who pleaded guilty to murdering six of her newborn infants over the course of a decade was sentenced Monday to 15 years to life in prison.

Megan Huntsman confessed to suffocating or strangling the babies while she was suffering from methamphetamine and alcohol addiction, according to police.

The six infants’ remains were found in April 2014 wrapped in old towels, shirts and plastic bags inside boxes in the garage in Pleasant Grove, a suburb just north of Provo. The body of a seventh infant was discovered disposed of in the same way but authorities have said they believe that child was stillborn.

Police have said Huntsman secretly gave birth to all seven without medical assistance at the house after apparently managing to conceal her pregnancies from the outside world.

Huntsman was not eligible for the death penalty because the murders, which took place between 1996 and 2006, predate changes in the law that would have made the offense a capital crime in Utah.