Legal Question in DUI Law in Washington

Not exactly. Washington doesn't have a 'no contest' option.

Entering a deferred is neither a guilty plea, nor a not guilty plea. The defendant has to sign an affidavit that they are 'not innocent' of the charges, but they never plead guilty. And at the end, the case is dismissed. It stays on the driver's record, and on the criminal record, but the defendant can legally say the case was dismissed. In the deferred context, however, many agencies still treat the driver as though they had been found guilty.

Deferred is a very complicated legal mechanism. Talk to a lawyer at length to make sure you understand all the consequences if you are considering resolving a case with a deferred prosecution.