Steven Kent Smith v. State, 01-15-00805-CR

Late-night police encounter: Officer Mulato observed Smith make an offensive gesture, then followed him without activating lights; Smith followed and drove erratically in a parking lot and on the road.
After about two miles, Smith made a U‑turn and failed to signal a lane change; Officer Mulato then stopped him.
On contact, officers observed slurred speech, odor of alcohol, red/glassy eyes, and disheveled appearance; Smith admitted drinking three rum-and-cola drinks.
Sergeant Morton administered HGN and observed six clues; other field tests produced additional clues; breath test later showed BAC 0.134.
Defense moved to suppress field-sobriety evidence, statements, and breath results; trial court excluded some testimony by Officer Mulato about the tests but denied suppression otherwise and submitted case to a jury, which convicted Smith of DWI.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether a jury instruction under art. 38.23 was required on legality of the stop	Smith: testimony raised a factual dispute whether the stop was motivated by suspicion of intoxication (requiring 38.23 instruction)	State: stop was supported by an objective traffic violation (failure to signal) so motive immaterial	Court: No instruction required; undisputed failure-to-signal provided objectively valid basis for stop
Whether stop and subsequent arrest should have been suppressed for lack of reasonable suspicion/probable cause	Smith: officer intended to stop him earlier and lacked grounds; claims lack of probable cause for arrest	State: Officer observed traffic violation; Sergeant Morton’s observations and HGN provided probable cause for arrest	Court: Trial court did not err; observed failure to signal justified the stop and Morton’s observations supported probable cause
Preservation of suppression challenge on appeal	Smith: preserved complaint via motions during trial and directed-verdict motion	State: argued waiver for lack of specific timely objection	Court: Smith preserved the issue adequately for appeal
Whether failure to signal is too minor to support stop	Smith: minor violation insufficient for reasonable suspicion	State: actual failure to signal is a violation and provides objective justification	Court: Prior cases relied on by Smith are distinguishable; failure to signal supported the stop

Madden v. State, 242 S.W.3d 504 (Tex. Crim. App. 2007) (standard for when art. 38.23 jury instruction is required)
Whren v. United States, 517 U.S. 806 (U.S. 1996) (objective traffic violation suffices for constitutional reasonableness of stop regardless of officer's subjective motive)
Walter v. State, 28 S.W.3d 538 (Tex. Crim. App. 2000) (stopping vehicle reasonable when officer has probable cause of traffic violation)