In State v. Brown, Division III of the Court of Appeals considered the fairly mundane issue of the turn signal requirement.   In the case, the defendant properly signaled his movement from his travel lane to the left turn lane.  But the defendant didn't signal after getting into the travel lane (The court reasoned it was probably because straitening the wheel caused the turn signal to cycle off).   After the left turn, the officer stopped Brown for failing to signal the turn, and later arrested him for DUI.   In a 2 to 1 split, the Court held the stop was illegal.   The majority reasoned there wasn't enough time to comply with the law, there was no requirement to give the signal once the driver was in the left turn lane, and because there was no evidence the turn caused any public safety issue by affecting other traffic. 

Read the full case here:  State v. Brown (Jan 17, 2019)

The court's reasoning was largely based on its interpretation of legislative history.  Typically, a court would not engage in such an analysis unless the plain language of the statute is ambiguous. 

The Benton County prosecutor's Office is considering an appeal to the State Supreme Court.  The opinion adds requirements not explicitly in the turn-signal statute, making it more difficult to enforce.