CALDWELL, Idaho (AP) — A southwest Idaho man who killed his girlfriend and buried her body in a cornfield has been sentenced to life in prison. The Idaho Press-Tribune reports that 40-year-old Alfredo Martinez of Nampa received the sentence Monday and must serve at least 20 years before becoming eligible for parole.

Martinez pleaded guilty in May in 3rd District Court to second-degree murder in the Aug. 15, 2014, death of 36-year-old Selena Thomas of Nampa. Court documents say Martinez beat Thomas with a hammer, then pushed her and she hit her head on a dresser.

Co-defendant Jose Cruz Flores of Nampa pleaded guilty earlier this month to felony destruction of evidence and failure to report a death after admitting he helped get rid of a weapon and lied to police.

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