Oral fluid drug testing (collecting saliva and testing it for the presence of drugs) is expanding in both criminal justice and workplace settings, and Texas is actively developing its use in roadside DWI investigations. Understanding what oral fluid testing can and cannot show, how it differs from urine and blood testing, and where its reliability can be challenged is increasingly important for defense attorneys and defendants facing drug-related charges.
What Oral Fluid Testing Detects
Oral fluid testing detects the parent drug (the active substance itself) rather than the metabolites that appear in urine after the drug has been processed by the body. This is a fundamental difference from urine testing. THC, the psychoactive component of cannabis, appears in oral fluid shortly after use and is detectable for a shorter window than in urine. Cocaine and its active metabolite appear in oral fluid for a brief period after use. Methamphetamine and MDMA are detectable in oral fluid for hours after use.
The detection window advantage of oral fluid over urine is that it more closely correlates with recent use: oral fluid THC is typically detectable for 4 to 8 hours after use in occasional users, and for longer periods in heavy chronic users, but generally not for the weeks that urine THC can remain positive after cessation. This makes oral fluid a potentially better indicator of recent use than urine, though the correlation with impairment is not established.
The Impairment Question
Oral fluid testing can detect the presence of drugs. It cannot establish impairment. The presence of a drug in oral fluid at a detectable concentration does not indicate that the person is currently impaired by that drug. This is the same fundamental limitation that applies to all biological drug testing methods, but it is especially acute with oral fluid because the detection window is shorter and often closer in time to actual use.
For cannabis specifically, the relationship between oral fluid THC concentration and driving impairment has not been established through scientific validation. Studies have shown that THC can be detected in oral fluid in concentrations above proposed legal thresholds in individuals who are not impaired by the drug. The Fitzgerald et al. (2025) study in Clinical Chemistry documented that regular cannabis users can have blood THC concentrations exceeding per se limits after 48 hours of abstinence without evidence of driving impairment. These findings are relevant to oral fluid testing in the same way: detection does not equal impairment.
The Two Devices Law Enforcement Is Actually Using
When an officer administers an oral fluid roadside test, they are almost certainly using one of two devices. Both are widely evaluated in state pilot programs. Both have documented limitations that are directly relevant to defense challenges.
Abbott SoToxa™ Oral Fluid Mobile Test System
The SoToxa is a handheld analyzer manufactured by Abbott (formerly the Alere DDS2). The officer inserts an oral swab into the device and receives a result in approximately five minutes. The current version screens for seven drug classes: THC, cocaine, opioids, amphetamine, methamphetamine, benzodiazepines, and fentanyl. It reports only a positive or negative result for each panel. No quantitative concentration is provided.
The SoToxa is designated Forensic Use Only by Abbott, meaning it is not designed for clinical diagnostic or workplace settings. Abbott’s own product documentation states that “a positive test result should be confirmed by a second test method such as GC-MS or LC-MS.”
The SoToxa’s THC assay has been a specific point of scrutiny. A DOT-commissioned evaluation found that the DDS2 (the predecessor device) met overall ROSITA performance requirements in aggregate, but the THC assay specifically did not meet those requirements. The SoToxa is the device most commonly discussed in Texas’s oral fluid pilot program development.
Dräger DrugTest 5000™
The Dräger DrugTest 5000 (DDT5000) is a fully automated analyzer using ready-to-swab cassettes. It screens for seven substances: amphetamine, methamphetamine, cocaine, opiates, benzodiazepines, THC, and methadone. Like the SoToxa, it produces only a qualitative positive or negative result per drug class, with no numerical concentration output. Dräger’s own manual requires a second sample submitted to an accredited laboratory for GC-MS confirmation before any result can be used as forensic evidence.
The DDT5000’s real-world performance has been evaluated in peer-reviewed literature with findings that are significant for defense purposes. A Norwegian study published in the Journal of Analytical Toxicology examined the device’s performance against blood concentration data from 369 drivers suspected of drug-impaired driving. The study found that when the DDT5000 produced positive cocaine results, 87.1 percent were false positives when compared against blood concentrations below Norwegian legal per se limits. Dräger has not published a direct response to this finding in the scientific literature, and no device modifications addressing the cocaine assay performance have been publicly announced.
A critical gap in both the SoToxa and the DDT5000: neither device screens for fentanyl in their standard panels (though a version of SoToxa now includes a fentanyl panel). Alabama’s five-year oral fluid program review found that confirmation testing detected fentanyl in 69 cases that the roadside devices had no capacity to flag which is a significant public safety gap during an ongoing opioid crisis, and a meaningful limitation on what a negative oral fluid screen actually means.
Case Results
The Third Device: Randox Evidence MultiSTAT™
A third device, the Randox Evidence MultiSTAT, has been evaluated in some state programs including Alabama’s comprehensive oral fluid program. It screens for a broader panel of substances and uses a different analytical platform than the Abbott and Dräger devices. It is less commonly discussed in Texas program development but may appear in defense cases depending on which jurisdiction’s equipment is used.
Roadside vs. Confirmatory Testing
Roadside presumptive oral fluid tests (whether SoToxa, DDT5000, or any other device) are screening tests only. They produce positive or negative results, not concentrations. A positive roadside oral fluid test establishes probable cause for further investigation; it does not establish that a controlled substance is present in a forensically confirmed quantity.
Confirmatory testing by LC-MS/MS or GC-MS provides a specific, quantitative result. But confirmation requires proper sample collection procedures, validated analytical methods, intact chain of custody, and qualified analysts which are the same requirements that apply to any forensic toxicology analysis. The confirmatory analysis is where the defense examination of oral fluid evidence most frequently focuses.
Texas’ Oral Fluid Testing Program
Texas has been developing its oral fluid drug testing program through a pilot project examining the use of oral fluid testing in roadside DWI investigations. The program involves specific approved devices and protocols for sample collection and confirmation. The key defense issues in any oral fluid DWI case include: the specific device used for roadside screening and its known error rates; the sample collection procedure and whether it was followed; the time between sample collection and laboratory analysis; the laboratory’s analytical method and its validation for oral fluid matrices; the cut-off concentrations used and their scientific basis; and whether the positive result, even if accurate, establishes anything about impairment at the time of driving.
Drug Testing Conditions and Oral Fluid
Oral fluid testing is also used in probation and bond supervision drug testing programs. The shorter detection window compared to urine makes oral fluid more useful for detecting recent use, but it also means that a person who used cannabis several days before a test may test negative by oral fluid while still testing positive by urine. Understanding the relative detection windows of oral fluid and urine for specific substances is important context for defendants on supervision whose testing results are being used against them in revocation proceedings.
If forensic science evidence is central to your case, contact Deandra Grant Law for a free, confidential consultation. Managing Partner Deandra Grant and Partner Douglas Huff both hold the ACS-CHAL Forensic Lawyer-Scientist designation. Deandra Grant also holds a Master’s Degree in Pharmaceutical Science and a Graduate Certificate in Forensic Toxicology. Call (214) 225-7117 or visit texasdwisite.com.
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