LUMMI RESERVATION - A Swinomish tribal member has pleaded guilty to smothering his common-law wife to death during an argument in their Lummi Reservation home earlier this year, according to the U.S. Attorney's Office.

Kevin S. O'Leary, 55, pleaded guilty to second-degree murder Tuesday, Nov. 27, in U.S. District Court in Seattle.

On June 7, he smothered Valerie Jefferson, 60, with a pillow. Jefferson's family reported her missing to the Lummi Nation Police Department on June 11. Police arrived at the couple's Smokehouse Road apartment the next day, after O'Leary tried to kill himself by stabbing his stomach.

During a search of the home, police could smell decomposition coming from a bedroom and discovered Jefferson's body wrapped in a blanket under the bed. O'Leary and Jefferson had been together for more than 27 years.

According to his plea agreement, O'Leary and Jefferson had been arguing for several hours when he grabbed a pillow and held it tightly over her neck, pressing down until her body went limp. He then wrapped the body in a blanket and hid it under their bed.

As part of his plea agreement, prosecutors are recommending a sentence of no more than 15 years in prison for O'Leary, but U.S. District Judge Robert S. Lasnik could give him up to life in prison. His sentencing is set for March 8, 2013.

Reach ZOE FRALEY at zoe.fraley@bellinghamherald.com or call 756-2803.