A DWI case used to be an officer's word against the driver's. It is now a stack of data — most of it generated by machines, and much of it available to the defense. Brian Foley walks through the technology in this video.
Technology the State uses
Electronic warrants. An officer drafts a blood-warrant affidavit on a laptop, emails it to an on-call magistrate, and has a signed warrant in minutes. Refusal no longer prevents a chemical result. The affidavit, however, is a document — and errors in it can invalidate the warrant.
Body-worn and in-car cameras. Every word, every sobriety test, and every step from stop to booking is recorded. This is the State's best evidence when the driver looks impaired — and the defense's best evidence when the driver does not.
Interlock and portable monitors. Bond conditions in Harris County routinely require an ignition interlock or a portable breath device that photographs the user and reports results to the court. A SCRAM ankle monitor measures alcohol through the skin continuously. Violations are reported automatically.
Vehicle data. Modern cars record speed, braking, steering, and — in a Tesla — whether driver-assist was engaged. Crash cases increasingly turn on the event data recorder.
Technology the defense uses
The same video. Frame-by-frame review against the NHTSA manual is how field sobriety test "failures" are taken apart.
Rideshare and phone records. A driver who opened Uber at 1:12 a.m. and got behind the wheel only when no car was available has a different story than the offense report tells. Location data can also fix the timeline for retrograde extrapolation.
Lab data. Gas chromatograph output, calibration logs, and batch records for blood tests are discoverable, and they are where analytical errors live.
Breath machine records. Maintenance and calibration histories for the Intoxilyzer are public records and are subpoenaed in every breath test case.
The bottom line
More data means more to challenge. A DWI defense in 2025 is as much a technical review as a courtroom argument, and it rewards lawyers who know where the data lives. Brian Foley and Luis Baez served on the Vehicular Crimes Team when this technology was being adopted. See our Houston DWI attorney page or call or text (713) 703-1718.