The state Supreme Court has unanimously ruled that drivers must use their signal every time they turn or change lanes on a roadway.

Thursday’s ruling reverses a Court of Appeals ruling that said a signal is required only when public safety is affected. The high court ruled that the plain language of the law requires drivers “to ensure turns and lane changes are done safely and with an appropriate turn signal."

The ruling was issued in the case of David Brown, who was arrested for driving under the influence in Kennewick in March 2015. State patrol officers pulled him over after he briefly turned on his left turn signal while approaching a light in a designated left turn lane but turned it off and did not reactivate it while at the light or making the turn. He was arrested after his breath test showed .26 breath alcohol content, more than triple the legal limit.

Brown had argued that the evidence of the breath test should be suppressed because the underlying traffic stop was without cause, and a lower court agreed and dismissed the case. The only issue before the Supreme Court was whether Brown violated traffic laws. The case now goes back to the lower courts to proceed in accordance with the high court's guidance on the initial stop.