The issue before the court, according to their summary, was "Does failure to maintain a single lane of traffic while driving need to be considered 'unsafe' before it can constitute an offense under §545.060(a) of the Transportation Code?" The result: "A plurality of the court agreed that a driver does not have to both fail to maintain a single lane of traffic AND attempt to move from that lane in an unsafe manner before it can be considered an offense. Either of these actions is enough to support a police officer’s stop and temporary detention."
Read Judge Yeary's plurality opinion, a concurrence by Judge Richardson, and dissents by Judges Keasler (joined by Johnson and Hervey, of all combinations) and Newell in a case which split the court along unusual fault lines, and for that reason may be worth particular attention.
TDCAA's commentary notes that this prosecution-friendly decision overturned prior precedents:
Failure to drive within a single lane of traffic is a very common reason for stopping motorists, especially in driving while intoxicated (DWI) cases. This decision expressly disagrees with two prior court of appeals decisions and will be very helpful for law enforcement. The court re-emphasizes (if it still needed emphasis) that an officer does not need probable cause, but only reasonable suspicion, to conduct a traffic stop. The court also upheld the officer’s actions based upon reasonable suspicion to investigate for DWI. All prosecutors need to read this decision.Some liberty-oriented legislator ought to take a closer look at this. There should be some public-safety reason for dubbing lane wobbling a traffic offense; otherwise, this just becomes an almost-universal pretext to pull people over. Bad decision from a preserve-the-Fourth-Amendment perspective.