If you are asking on behalf of yourself or someone you love who is suspected of doing this, it is very unwise to post a question about a specific case on an online forum like this. If the police or DA in WA got wind of this they could easily find out who posted the question.
My advice would be to find out from the Avvo folks how to delete the question and do so ASAP. Then contact a criminal defense lawyer and discuss your concerns during a confidential conversation.
If you are contacted by the police, ask for a lawyer. Do NOT give a statement until you have discussed this matter with your lawyer.
A person is guilty of Rendering Criminal Assistance in the First Degree if he or she renders criminal assistance to a person who has committed or is being sought for murder in the first degree.
Rendering Criminal Assistance in the First Degree is a "C" felony unless it is established by a preponderance of the evidence that the actor is a relative as defined in RCW 9A.76.060. Then it is a Gross Misdemeanor.
Assuming no prior felonies or points, the standard range for the C felony offense is 6 to 12 months in jail. If it is a gross misdemeanor Rendering, then the maximum jail sentence is 365 days in jail and a $5000 fine.