A federal judge in Portland, Oregon, has sentenced a woman to life in prison for her role in a Pacific Northwest killing spree that authorities say was part of a white supremacist scheme.

Holly Grigsby apologized Tuesday to friends and relatives of the victims. Grigsby said she realized that any explanation for her behavior would come across as an excuse.

Grigsby and her boyfriend -- David "Joey" Pedersen -- were  arrested in 2011 after the deaths of Pedersen's father and stepmother in Everett, Wash., an Oregon teenager and a California man.

Grigsby pleaded guilty in March to racketeering charges connected to the four killings, and the plea agreement called for a life sentence with no chance for release.

Joey Pedersen is scheduled to be sentenced next month.