CALDWELL (AP) - A southwest Idaho man who killed his girlfriend and buried her body in a cornfield has been sentenced to life in prison.

Alfredo Martinez, 40, of Nampa received the sentence Monday and must serve at least 20 years before becoming eligible for parole.

"I'm sorry. I apologize, and I know it's not enough," Martinez said in 3rd District Court. "I see the hurt, the anger, the sadness, not just on one side of the courtroom but on both sides. It's because of my actions."

Martinez pleaded guilty in May to second-degree murder in the Aug. 15, 2014, death of 36-year-old Selena Thomas of Nampa.

Martinez beat Thomas with a hammer, then pushed her and she hit her head on a dresser, court documents say. Police said he put her body in a closet for two days before getting three others to help him bury the body near Melba.

Martinez took steps to hide the crime, Deputy Canyon County Prosecutor Monica Morrison said. Besides burying her body, he also got rid of bloody sheets, Thomas' cellphone, and removed a tracking device from her car.

Co-defendant Jose Cruz Flores, 25, of Nampa, who is a nephew of Martinez, 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. His sentencing is set for Sept. 14.

Jorge Luis Garcia of Nampa has pleaded not guilty to concealing or destroying evidence and failure to notify of a death. His trial is set for Sept. 14.

Daniel Francisco Sena, also of Nampa, has pleaded not guilty to concealing or destroying evidence. He is scheduled to go on trial on Aug. 25.