The State’s case against you may come down to one number produced by one machine, analyzed by one person, on one day. Most people never learn that the sample which produced that number still exists, that Texas law requires it to be preserved for a defined period, and that an independent laboratory can test it again. That option has a shelf life, and the 89th Texas Legislature just changed how that shelf life works.
Senate Bill 1660 amended Article 38.50 of the Texas Code of Criminal Procedure effective September 1, 2025, adjusting how crime laboratories handle the destruction of toxicological evidence in intoxication cases. Our DWI defense attorneys in Conroe track these procedural changes closely because they determine how long a genuine second look remains available. This article explains the retention framework, what SB 1660 changed, and how independent retesting actually works in a Montgomery County case.
What Article 38.50 Requires
Article 38.50 governs the retention and preservation of toxicological evidence in cases involving intoxication offenses under Chapter 49 of the Penal Code. That includes driving while intoxicated, boating while intoxicated, intoxication assault, and intoxication manslaughter.
The statute sets minimum retention periods tied to the seriousness of the offense and the status of the case. Evidence in a pending case must be retained while the case remains open. After a conviction, retention obligations continue for a period tied to the sentence. The purpose is to make sure a sample is still available if a defendant later challenges the result.
Crucially, the statute is a floor, not a ceiling. Laboratories may retain evidence longer, and many do, but a defendant should never assume a sample will be there indefinitely.
What SB 1660 Changed
Before September 1, 2025, the notification and destruction process left prosecutors with a short window to object before a laboratory disposed of a sample. SB 1660 restructured that process in two practical ways.
First, crime laboratories must now provide annual notification to the relevant prosecuting attorney identifying toxicological evidence whose retention period is expiring. That converts an ad hoc process into a scheduled one.
Second, the window for the prosecutor to respond before destruction was extended to 90 days. A longer response period reduces the risk that evidence is destroyed while a case is still in motion, which matters most in appellate and post-conviction contexts.
The change applies to evidence whose retention period expires on or after September 1, 2025. It is a procedural adjustment rather than a dramatic shift, but for a defendant seeking retesting late in a case, it can be the difference between having a sample and having a paper record of one.
How Independent Retesting Works
When blood is drawn under a warrant in Montgomery County, two vials are typically collected. The State tests one. The second frequently remains sealed. That second vial is the basis for an independent test.
The process runs roughly as follows.
- Discovery. Your attorney requests the full laboratory file under Article 39.14, including bench notes, chromatograms, calibration records, maintenance logs, and analyst certifications.
- Review by an expert. A forensic toxicologist examines the data before anyone asks for a retest. Sometimes the existing records reveal the problem and no retest is needed.
- Motion for independent analysis. Counsel moves the court for an order permitting release of the remaining specimen to a designated accredited laboratory.
- Chain of custody transfer. The sample moves under documented custody to the defense laboratory.
- Analysis and report. The independent laboratory performs its own testing and issues findings.
Retesting is not free, and it is not always the right call. When the State’s result is 0.21 and the driving was severely impaired, a second test confirming 0.20 helps nobody. When the result is 0.09, the collection was sloppy, and the sample sat in a warm evidence room for four months, a retest can be decisive.
What retesting can reveal
Blood samples degrade. Improper preservation allows microbial fermentation, which can generate ethanol in a sample that did not originally contain it, or elevate a concentration that was originally lower. Gray-top vacutainers contain sodium fluoride as a preservative and potassium oxalate as an anticoagulant precisely to prevent this. An expired tube, an underfilled tube, or a tube that was never properly inverted after collection can allow the process to proceed.
A retest performed months later will typically show a lower concentration than the original if the sample was properly preserved, because ethanol slowly oxidizes. A retest showing a materially higher value than the original raises serious questions about preservation and storage.
Where Blood Cases Break Down Beyond the Number
In our experience, the laboratory result is often the least productive place to focus. These issues appear more frequently.
- Collection personnel and setting. Transportation Code Section 724.017 restricts who may draw blood and requires a sanitary place. Draws performed at jail intake or in mobile units invite scrutiny.
- Antiseptic used. Alcohol-based swabs at the draw site are a documented contamination concern and a training violation.
- Storage temperature and duration. Evidence rooms are not always refrigerated, and Texas summers are unforgiving.
- Chain of custody gaps. Every transfer must be documented. Missing signatures and unexplained time gaps are common in high-volume counties.
- Analyst qualifications and error history. Accreditation records, proficiency testing results, and corrective action reports are discoverable.
- Retrograde extrapolation. If the draw happened ninety minutes after driving, the State must argue backward to your concentration at the wheel. That calculation rests on assumptions about absorption rate, stomach contents, and drinking pattern that frequently do not fit the facts.
When Retesting Is Worth Pursuing
Independent analysis is a tool, not a reflex. These are the fact patterns where it tends to earn its cost.
- A borderline result. A reported concentration between 0.08 and 0.11 leaves room for measurement uncertainty and preservation error to matter. A result well above that range rarely moves enough to change anything.
- A long interval between collection and analysis. Months in an evidence room, particularly through a Texas summer, is the classic setup for a preservation challenge.
- Documented collection problems. An expired tube, an underfilled vial, a missing inversion, or an alcohol-based swab noted in the records all justify a closer look.
- A gap between the number and the observations. When video shows clear speech, steady balance, and normal responses alongside a high reported concentration, something in the chain deserves scrutiny.
- Chain of custody irregularities. Unexplained time gaps or missing signatures undermine confidence in what was actually tested.
- Felony exposure. Where the charge carries prison time, the calculus on expert cost changes entirely.
Conversely, when the result is far above the threshold, the collection records are clean, and the driving evidence is strong, the money is usually better spent elsewhere in the defense.
Timing Is the Whole Game
Retention periods run, laboratories process destruction lists, and cases that sit dormant lose options. If you are considering post-conviction relief or an appeal in an intoxication case, the availability of the underlying sample should be confirmed early rather than assumed.
For a pending case, the practical guidance is simpler. Request the laboratory file as soon as counsel is retained, have it reviewed by a qualified toxicologist, and make the retest decision before the case reaches a plea posture. Once a plea is entered, the leverage that an independent analysis creates is gone.
Montgomery County Considerations
Because Montgomery County runs an aggressive blood warrant program, the volume of toxicological evidence flowing through regional laboratories is substantial. High volume produces backlog, and backlog produces delay between collection and analysis. That interval is exactly when preservation problems develop.
It also means turnaround on results is slow. Clients frequently wait months after arrest before a case is formally filed, which feels like limbo but is simply the laboratory queue. Understanding how the DWI process moves in Texas helps set realistic expectations, and the penalty exposure at stake is outlined on our page covering DWI penalties and fines.
Frequently Asked Questions
Can I get my blood sample retested in a Texas DWI case?
Usually yes, if a second vial remains and the retention period has not expired. Your attorney files a motion for independent analysis and the sample is transferred under court order to an accredited defense laboratory.
How long does Texas keep DWI blood evidence?
Retention periods under Article 38.50 depend on the offense level and the status of the case. Pending cases require retention throughout. SB 1660 added annual laboratory notification to prosecutors and extended the pre-destruction response window to 90 days.
Does a lower retest result get my case dismissed?
Not automatically, but it creates meaningful reasonable doubt and often changes negotiating posture significantly. The two results together also open questions about the laboratory’s reliability.
How much does independent retesting cost?
Costs vary by laboratory and scope. Expert review of the existing file is usually the first step and is considerably less expensive than a full retest. Many cases are resolved on the file review alone.
What if the sample was already destroyed?
Destruction of evidence a defendant was entitled to examine can support a motion challenging the remaining results, depending on when destruction occurred and whether proper procedures were followed.
Can blood alcohol increase after the draw?
Yes, under specific conditions. Inadequate preservative combined with bacterial contamination and warm storage can produce ethanol within the tube. This is precisely why collection and storage records matter.
Your Next Step
A blood result is a scientific claim, and scientific claims can be tested. The sample that produced the number against you may still be sitting in a laboratory refrigerator right now, but it will not be there forever.
Griffin & Cain, Attorneys at Law obtains the complete laboratory file in every blood case and works with qualified forensic experts when the data warrants it. Schedule your consultation with criminal defense attorney Stella A. Stevens to have your blood evidence reviewed while the sample is still available. Contact our Conroe office today. We represent clients across Montgomery and Walker Counties, including Conroe, The Woodlands, Montgomery, and Huntsville.
