UBCNews - Business - Can DWI Blood Tests Be Wrong? Challenging Lab Results in Texas Courts

Episode Date: February 25, 2026

So, you know when someone gets arrested for a DWI, prosecutors love to bring out blood test results like they're the ultimate trump card, right? But here's the thing that might surprise a lot of people - these tests can actually be challenged in court. What makes blood evidence so powerful in the first place? Texas Criminal Defense Group City: Lubbock Address: 1001 Texas Ave. Website: https://texascriminaldefensegroup.com/

So, you know, when someone gets arrested for a DWI, prosecutors love to bring out blood test results like they're the ultimate Trump card, right? But here's the thing that might surprise a lot of people. These tests can actually be challenged in court. What makes blood evidence so powerful in the first place? Well, prosecutors often prefer blood tests in DWI cases because they're seen as reliable, and they can detect not just alcohol but drugs to,

marijuana, prescription meds, controlled substances, A breathalyzer can't do that. Blood samples give precise blood alcohol concentration levels or BAC, which makes them the centerpiece of many prosecutions. But here's what people need to understand. Reliable doesn't mean infallible. Right, exactly. And I think that's where defense attorneys come in.

What are some of the main ways that blood test results can actually be wrong or challenged? There are multiple angles. First, you've got procedural. errors during the blood draw itself, expired collection kits, improper sterilization, inadequate venipuncture techniques, then there's chain of custody issues. If the blood sample wasn't tracked correctly from the moment it was drawn to the lab and through analysis, you could have contamination or even mix-ups, and gas chromatography, which is the testing method, can produce errors if the equipment isn't calibrated properly or if the sample isn't handled right.

Mm-hmm, that makes sense. So the issue goes beyond whether the number says 0.08 or above. The question is how that number was obtained. What about the legal side? Can police just take your blood without permission? Great question. A blood draw is considered a search under the Fourth Amendment, so generally law enforcement needs either your consent or a warrant.

There are some narrow exceptions, like exigent circumstances or if the driver is unconscious, but even those can be contested in court. In Texas, we have implied consent laws, which means that by driving on public roads, you've agreed to submit to chemical testing if lawfully arrested for DWI. But that doesn't mean police can automatically force a test. Furthermore, under the new 2026 statutes, police can now execute warrants across county lines, but this increased speed often leads to jurisdictional errors that a skilled attorney can identify.

I see. Interesting. If you refuse, you face an automatic driver's license suspension, 180 days for a first refusal, two years if you've had a previous refusal or alcohol-related contact in the last 10 years. But refusal doesn't automatically validate an unlawful blood draw. If officers violated your Fourth Amendment rights, that evidence can sometimes be suppressed. So to everyone listening, have you ever wondered if those blood test results could be wrong? because the answer might surprise you. That point about Fourth Amendment protections

and constitutional violations sets up our next piece, how labs actually process these samples. But first, a quick word from our sponsor. If you're facing DWI charges in Dallas or anywhere in Texas, the Texas Criminal Defense Group brings 27 years of board-certified

criminal defense experience to your case. With DWI cases making up over 64% of their practice, Their team uses a data-driven approach, reviewing police reports, dash cam and body cam footage, and utilizing the services of an in-house forensic toxicologist to analyze blood test evidence in every case. They offer a flat fee structure that includes trial representation and flexible payment plans. Learn more at Texas Criminal Defense Group.com. Picking up on those constitutional violations and Fourth Amendment protections, how do defense attorneys handle the science when they're scrutinizing blood test results?

Well, this is where forensic toxicologists become essential. They review laboratory procedures, instrument calibration, and the scientific validity of the results to identify potential flaws. For example, if a blood sample isn't properly preserved, fermentation can occur, which artificially increases the alcohol concentration. This is a recognized defense strategy used in Texas cases where improper sample handling has led to unreliable results. Wow, that's a pretty significant error.

What else do toxicologists look for? They'll examine calibration and maintenance records of the gas chromatograph used for BAC analysis. Improper maintenance can lead to skewed results. They also check whether the person who drew the blood was properly qualified, whether the equipment used was appropriate, and whether the testing methods followed accepted scientific protocols. Crime labs operate under-established protocols for blood alcohols. alcohol analysis, and any deviation from those can be grounds for challenging the results.

I actually had a case early in my career where we found the phlebotomist had let their certification lapse three months before the blood draw. That was enough to successfully challenge the admissibility of the evidence. Oh, wow, that's the kind of detail that makes all the difference. So to everyone listening, if you've been charged with a DWI and blood evidence is involved, there are multiple layers that can be questioned. What about the actual warrant? process? How does that work? If police have probable cause, strong signs of intoxication, they can request a warrant from a judge, even electronically. Once granted, they can legally take your blood even if you refuse, but effective defense strategies scrutinize the

warrant's validity. Was there truly probable cause? Was the warrant properly executed? These are questions that need answers. You know, some officers will say they smelled alcohol, but that alone isn't always enough for probable cause. Right. And I imagine there's also the human element. Mistakes happen in labs. People mishandle samples. Absolutely.

Experts know that errors happen more often than people think. Established guidelines exist for forensic blood alcohol analysis, highlighting best practices to ensure accuracy and reliability. When those aren't followed, results become unreliable. Defense attorneys often request to see. discovery of all lab reports, maintenance logs, and analyst certifications to scrutinize the entire testing process for noncompliance or errors. Think of it this way. Even the most sophisticated test is only as good as the person running it. Makes sense really does. And here's something that

might make you chuckle. I've seen cases where the blood sample got mixed up because someone wrote the wrong name on the vial. You'd think that's impossible in 2025, but here we are. That's funny if it weren't so serious. So we've established that blood tests aren't bulletproof. In other words, they're not infallible evidence. What about retrograde extrapolation? I've heard that term thrown around. Ah, yes. Retrograde extrapolation is a method used to estimate BAC at the time of driving based on a later blood test. This approach is commonly contested because it has inherent variability. Everyone metabolizes alcohol differently. factors like body weight, gender, food intake, and the time between driving and the blood draw all affect the calculation.

Defense attorneys challenge this method because it's not an exact science. Makes sense. And beyond the science, what are the real-world consequences people should know about if they're convicted of a first-time DWI in Texas? The long-term impact goes way beyond immediate penalties. You're looking at fines, jail time, license suspension, but also things people don't. don't always consider, dramatically increased auto insurance premiums that can double or triple for three to five years, professional harm if you need a clean record for work, damage to your community standing. The total cost often exceeds $15,000 when you factor in legal fees, increased insurance rates, probation fees, ignition interlocked devices, and mandatory DWI education programs. $15,000. That's a hefty price tag. And this is for a first offense?

Exactly. People think there's a fine and maybe a night in jail, but the ripple effects are significant. You face license suspension ranging from 90 days to a year. You have to maintain SR22 insurance, complete a 12-hour DWI education program within 180 days, possibly install an ignition interlock device, and if your back was 0.15% or higher, the charge upgrades from a Class B to a Class A misdemeanor, which increases penalties even more. So given all these stakes, what should someone do if they're facing a DWI charge based on blood test evidence? First, don't assume the blood test is accurate just because it's scientific. Challenge everything.

The legality of the traffic stop, the validity of the warrant if one was used, the administration of field sobriety tests, the chain of custody, the lab procedures, look for procedural errors at every step, and definitely consult with an attorney who has experience in this area, someone who understands both the legal and scientific aspects of challenging blood evidence. Definitely. I mean, the science is complex, the law is complex. You need someone who can work through both.

Any final thoughts for our listeners? Just this. A DWI charge can feel overwhelming, especially when prosecutors present blood test results as definitive proof. But remember, these tests are not beyond challenge. from questions about warrants to mistakes in testing or storage, there are many ways to fight back if your rights were violated. The key is acting quickly and getting knowledgeable legal help.

Great advice. Thanks so much for breaking all this down today. I think our listeners have a much clearer picture of how blood tests work in DWI cases and why they can be challenged. Until next time, stay informed and stay safe.