The Elko Daily Free Press reports 19-year-old Kody Cree Patten entered the plea Wednesday morning. He'd previously pleaded not guilty and was set for a July trial.
Patten and his then-girlfriend, Toni Fratto, were accused of the death of 16-year-old Micaela "Mickey" Costanzo.
Authorities say she was taken to a remote area near the Utah-Nevada border, where she was struck with a shovel and her throat was slit before she was buried in a shallow grave.
Fratto pleaded guilty to second-degree murder with a deadly weapon and was sentenced in April to up to life in prison.
Information from: Elko Daily Free Press
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