An operator intending to turn a vehicle right or left shall signal continuously for not less than the last 100 feet of movement of the vehicle before the turn. -- Tex.Transp.Code (1999) Sec. 545.104(b)
The Texarkana Court of Appeals, in Wehring v. State, ___ SW3d ___ (Tex.App.--Texarkana 2008, pet. filed) held that a driver must signal a turn, even if he is turning from a turn-only lane. According to the Court, the statute "does not include exceptions for those situations in which there is only one direction to turn." The opinion went on to state that "requiring the use of a turn signal while entering a turn-only lane and making the turn would lead to absurd results."
Of course the Court also noted that Mr. Wehring was speeding and that the officer could have stopped him for that offense instead.
The lesson, as always, is don't get behind the wheel of a car if you are intoxicated. Watch while you're driving around during the day and count the number of people who signal turns or lane changes. But, if you get behind that wheel late at night, especially in an area with a multitude of restaurants and bars, any little "slip" can lead to a traffic stop and change your life.