procedure for contesting traffic ticket, traffic infraction in WA state, suspended drivers license, illegal stop, probable cause

The mere fact that you were not written up for the illegal left turn does not make the stop illegal. To the contrary, the officer had problem cause to stop you, get your license and find out your were suspended. He thereafter has the discretion to issue you a summons for the illegal left turn (or not). In fact, he likely could add this charge back to the case prior to trial. Check with a Washington State traffic lawyer to confirm.

The basis for the stop was still legitimate, even if he did not issue you an infraction for the illegal turn. He is under no requirement to issue that traffic citation to you.

Many local attorneys will offer free consultations on criminal matters, such as yours, and you should take advantage of this as soon as possible.

I agree with Mr. Dichter. Consider yourself lucky that the officer gave you a break by not also writing a citation for the turn. No doubt the officer wrote the basis for the stop on the ticket for driving on a suspended license. So long as he or she can accurately testify as to the basis for the stop, the fact that you didn't get a ticket for it is no defense.