Michelle Anderson and her ex-boyfriend, Joseph McEnroe, are charged with killing Anderson's parents, Wayne, 60, and Judith Anderson, 61; her brother, Scott, and his wife, Erica, both 32; and the couple's two children, Olivia, 5, and Nathan, 3, inside the elder Andersons' Carnation home.
The lawyer, Stephan Illa, says Anderson has changed her mind after telling reporters last summer she was guilty and deserved to die.
Illa says King County Prosecutor Dan Satterberg is making a costly mistake in deciding to seek the death penalty against Anderson and co-defendant Joseph McEnroe if they are convicted of aggravated murder.
Satterberg says the magnitude of the crime requires that a jury have the option of execution.
The lawyer for McEnroe says he's disappointed by Satterberg's decision.
Prosecutors say Anderson and McEnroe killed Anderson's parents, brother and sister-in-law and their two young children. Anderson told detectives her brother owed her money and that she was upset because her parents did not take her side.