A Tucson woman accused of first-degree murder for the death of her 11-week-old baby has pleaded guilty to manslaughter.

Olivia Paige Martinez, 22, originally was accused of first-degree murder, two counts of child abuse and abandonment/concealment of a dead body after the January 2012 death of her daughter, Vanessa Martinez.

Martinez pleaded guilty to manslaughter on Thursday in Pima County Superior Court Judge Richard Nichols’ courtroom.

Defense attorney Bobbi Berry said Martinez’s boyfriend squeezed and shook the baby, causing grave internal injuries, including fractured ribs. Martinez then took the baby from her boyfriend, Jonathan Niles Kesterson, and brought the infant to bed without seeking medical care. Later that night, Berry said, Martinez realized the baby had difficulty breathing and died shortly after.

The couple then fled Tucson with the dead infant, burying her body in the desert near Casa Grande in the area of Toltec Road and Interstate 10.

Martinez and Kesterson later fled to San Diego, where they were arrested in April 2012.

Kesterson, 26, hanged himself in his Pima County jail cell in July 2012.

Contact reporter Patrick McNamara at 573-4241 or pmcnamara@azstarnet.com. On Twitter @pm929.