Blood Evidence
Blood Test Defense in Texas
A blood result carries more weight with a jury than a breath result, and it also leaves a longer paper trail. Every stage between the needle and the number is documented.
Since 2021 a blood draw taken over your refusal requires a warrant, which puts a sworn affidavit into the record as well.
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The warrant, and what it puts in the record
Where you refuse, police need a warrant before taking blood. Obtaining one means an officer swore an affidavit setting out the facts said to establish probable cause, and a magistrate signed it at a recorded time.
That document is now part of the case. What it claims, whether those claims match the video, and how much time passed between the stop, the affidavit and the draw are all checkable. An affidavit that describes driving the dash camera does not show is a problem for the State rather than for you.
Some categories of case allow a mandatory specimen under section 724.012(b), but that mandatory power is still subject to the warrant requirement. The two rules operate together rather than one overriding the other.
The refusal guide explains the difference between an officer-requested specimen, a refusal, and a later judge-signed warrant.
Who may take the sample, and where
Section 724.017 is specific about both, and specificity creates checkable requirements.
The draw record can identify the person who collected the specimen, that person's qualification under section 724.017, the collection site, the kit and vial identifiers, the condition of the seals, and the time each step occurred. Those details can be compared with hospital, booking, body-camera, and transport records to test whether the documented protocol matches the actual collection.
After collection, the laboratory packet may document transfers and storage, accession, the analytical run, quality-control results, validation, and analyst notes. Reviewing the complete chain tests whether the reported result can be tied to the specimen taken in the case and whether the run met the laboratory's own requirements. The accession record, transfer log, instrument sequence, controls, and analyst notes should describe one traceable specimen and one supportable analytical run rather than disconnected entries.
Qualified personnel only
A physician, qualified technician, registered nurse, licensed vocational nurse, or an authorized emergency medical technician or paramedic. Not an officer, and not anyone who happened to be available.
A sanitary place
The statute requires the draw be taken in a sanitary place. A roadside or the back of a patrol vehicle is not obviously that, and where it happened is a matter of record.
Chain of custody
Between the draw and the lab result the sample is handled, stored, transported and analyzed. Every transfer should be documented, and gaps in that record are real issues.
The sample still exists
This is the practical difference between blood and breath. A breath sample is gone the moment it is measured. A blood sample is physical evidence that continues to exist, and Code of Criminal Procedure article 38.50 governs its retention.
That opens a route breath cases do not have: independent retesting of the State's own sample. It is a different mechanism from the additional specimen right under section 724.019, which applies only to someone who submitted to the officer's test and has to be arranged within two hours of arrest.
Knowing which of the two applies to your case matters, because they arise at different times and produce different evidence. You are also entitled to full information about the analysis on request under section 724.018.
Where blood cases differ on timing
Blood results come back weeks later, so DPS mails the license suspension notice rather than handing it over at arrest.
That makes the deadline 20 days from mailing rather than 15 from arrest, and it is easy to miss if you have moved. See the 15 day ALR deadline.
Related pages
Breath test defense
What the Intoxilyzer 9000 measures and the records behind a result.
Drug DWI and prescriptions
No alcohol required, and a valid prescription is not a defense.
Intoxication manslaughter
A second degree felony, with 2025 changes creating first degree exposure.
Blood test questions
Can police take blood without my consent?
Not without a warrant, since 2021. Certain categories of case allow a mandatory specimen under section 724.012(b), but that is still subject to the warrant requirement.
Who is allowed to draw the blood?
Section 724.017 limits it to a physician, qualified technician, registered nurse, licensed vocational nurse or authorized paramedic, in a sanitary place.
Can my sample be retested?
Often, yes. Blood is physical evidence that continues to exist, and article 38.50 governs retention. That is a route breath cases do not have.
Why did my license notice arrive in the post?
Because blood results take weeks. DPS mails the notice once they come back, and the deadline to contest becomes 20 days from mailing rather than 15 days from arrest.