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Stuart Johnson, Stuart Johnson, Deseret News
Kody Patten sits while his attorney, John Ohlson, argues his case in 4th District Judicial Court in Elko, Nev., Friday, Jan. 17, 2012. Patten is charged with first-degree murder in the death of fellow West Wendover High School student Micaela Costanzo, 16.

LAS VEGAS — The lawyer for one of two teens accused in the March 2011 killing of a Nevada classmate said Friday that the 19-year-old will plead guilty to first-degree murder.

Attorney John Ohlson told The Associated Press that Kody Cree Patton will enter the plea Wednesday in Elko.

"It was the sensible thing to do," Ohlson said Friday, adding that if some of the details about the killing came out at trial, "it would be difficult to avoid the death penalty."

Patten and his then-girlfriend, Toni Fratto, were accused in the death of 16-year-old Micaela "Mickey" Costanzo, who was taken to a remote area near the Utah-Nevada border after track practice at West Wendover High School on March 3, 2011.

Authorities said she was struck in the head with a shovel and her throat was slit before she was buried in a shallow grave.

Patten and Fratto were also accused of burning some of the girl's personal items in another location.

Fratto hadn't been a suspect until she offered a confession to Patten's defense attorney. In the recording, she told lawyers Micaela wanted to date Patten, but he didn't want anything to do with her.

Fratto, now 19, pleaded guilty to second-degree murder with a deadly weapon and was sentenced in April to up to life in prison. She will be eligible for parole after serving 18 years.

Patten had previously pleaded not guilty and was set to go to trial in July. As part of her plea agreement, Fratto had agreed to testify against him.

Fratto's mother, Cassie Fratto, declined to specifically address Patton's pending plea in a Friday interview with the Associated Press. But she described her daughter as a girl with a bright future, an active volunteer in her small community, who became a victim in an emotionally and physically abusive relationship with Patten.

"Toni's not a monster," Cassie Fratto said, pointing out that her daughter came forward to accept responsibility for her role in the death. "She got wrapped up with the wrong person."

In an interview with Anderson Cooper that was set to air Friday afternoon on the syndicated talk show "Anderson," Fratto was asked why she hit Costanzo with a shovel. She said Patten told her to "just do it, it's OK, just do it," adding that she was terrified and didn't know what to do. Fratto spoke from the jailhouse in Elko, where she is being held.

Ohlson dismissed the statements.

"The lengths people will go to to avoid responsibility," he said.