The case went to the jury before noon Tuesday in Everett without any word from Byron Scherf.
The Daily Herald reports defense lawyer Karen Halverson asked jurors not to be swayed "by the voices of vengeance or retribution."
Prosecutor Paul Stern reminded jurors of something Scherf told detectives in his confession, "If you take a life, you give a life."
The jury took about an hour Thursday to convict Scherf of aggravated murder for strangling Jayme Biendl (JAY'-mee BIN'-dul) with an amplifier cord in January 2011 in the chapel at the Washington state Reformatory at Monroe.
The 54-year-old convicted rapist was already serving life in prison without parole.