What changes
A second DWI is a Class A misdemeanor: up to one year in county jail, a fine up to $4,000, and a statutory minimum jail term of thirty days on conviction. An ignition interlock is required as a condition of bond, not just as a condition of probation, which means it goes on your vehicle before your case is resolved.
The license suspension is longer. Probation terms are stricter. And a second conviction sets up a third as a felony, which is the real reason to fight it hard now.
What counts as a prior
More than people expect. A prior DWI from any state counts. So does a BWI, boating while intoxicated, which catches people who paid a lake charge years ago thinking it was a ticket. Deferred adjudication on certain intoxication offenses can count. There is no lookback window in Texas for DWI enhancement, so a conviction from twenty years ago still counts.
The first thing I do on a second offense case is examine the prior itself. If the earlier plea was taken without counsel, or without a proper waiver, the enhancement may be attackable. That is technical work and it is where these cases are sometimes won.
The blood evidence
Second offense cases are more likely to involve a blood warrant and a lab result, and prosecutors are less inclined to move on them. That makes the quality of the lab package matter more, not less. How blood testing gets challenged.