Dallas DUID Lawyers

Where the Evidence Goes: Dallas County Laboratory Routing

Dallas Police Department Arrests

Blood and specimen samples collected in DPD arrests are typically sent to the Southwestern Institute of Forensic Sciences (SWIFS) on North Stemmons Freeway for toxicological analysis. SWIFS performs drug identification and quantification using immunoassay screening followed by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) confirmation. Understanding SWIFS’s specific methodology, analyst qualifications, and quality assurance protocols is specific knowledge that matters in Dallas DUID cases involving DPD arrests.

Outlying Dallas County Agency Arrests

When the arresting agency is one of the outlying Dallas County departments (ex. Irving, Garland, Mesquite, Grand Prairie, Lancaster, Duncanville, DeSoto, Cedar Hill, Balch Springs, Hutchins, Wilmer, or others) the laboratory routing is not fixed. Many of these agencies send specimens to the Texas DPS Crime Lab in Garland. Others use different accredited facilities. The first step in any Dallas County DUID defense is identifying which laboratory analyzed the specimen and obtaining the complete analytical records from that specific facility.

The Screening vs. Confirmation Distinction

Drug testing in DUID cases typically begins with an immunoassay screen. Immunoassay screens are sensitive but not specific. They detect drug classes by antibody-antigen reaction and can produce false positives from cross-reactive compounds. A positive immunoassay screen does not identify a specific drug or a specific concentration. Confirmatory testing by GC-MS or LC-MS/MS is required for specific identification and quantitation. A prosecution that proceeds on the basis of a screen result alone, without GC-MS or LC-MS/MS confirmation, is proceeding without confirmation of what substance is actually present.

The Pharmacokinetic Defense: Why Concentration Doesn’t Equal Impairment

The pharmacokinetic profile of a drug (i.e. how it moves through the body after ingestion) determines the relationship between the blood concentration measured in a SWIFS or DPS lab result and the actual impairment experienced by the driver at the time of the stop.

THC.  THC is lipophilic and is distributed out of the bloodstream rapidly after consumption. Blood THC concentrations can reflect redistribution from fat stores during exercise or caloric restriction rather than recent use. That means a positive blood THC result does not reliably indicate when cannabis was consumed or whether the driver was impaired at the time of the stop. The THC redistribution phenomenon is documented in peer-reviewed literature and directly relevant to cannabis DUID cases.

Benzodiazepines.  Tolerance develops with regular therapeutic use of benzodiazepines. A person who has taken a prescribed benzodiazepine at a stable therapeutic dose for months may have measurable blood concentrations without meaningful functional impairment. The concentration, the metabolite profile, and the individual’s documented tolerance are all relevant to whether impairment can be proven.

Prescription opioids.  Chronic opioid users develop tolerance that significantly alters the relationship between blood concentration and impairment. A blood opioid concentration that would impair an opioid-naive person may not indicate impairment in a person on a stable, medically supervised regimen.

Evaluating these pharmacokinetic arguments requires the kind of training in drug metabolism, pharmacokinetics, and toxicology that Deandra Grant’s Master’s Degree in Pharmaceutical Science provides. Most defense attorneys can challenge the chain of custody or the DRE protocol. Fewer can independently evaluate whether the blood concentration the lab reported supports a finding of impairment at the time of driving.

The ALR Hearing in Dallas DUID Cases

A DUID arrest, like any DWI arrest, triggers the 15-day ALR deadline . The administrative license revocation proceeding runs parallel to the criminal case and must be requested within 15 days from the date of notice of suspension. Missing that deadline means an automatic license suspension regardless of what happens in the criminal case. In a DUID case, the ALR hearing is also an opportunity to take sworn testimony from the arresting officer and the DRE before the criminal case proceeds.

Speak With Deandra Grant Law About Your Dallas DUID Case

DUID defense in Dallas County requires knowing which laboratory analyzed your specimen, understanding that laboratory’s methodology and protocols, evaluating the DRE officer’s adherence to the evaluation protocol, and independently analyzing whether the drug concentration in the blood result supports a finding of impairment at the time you were driving. That analysis requires scientific training.

Deandra Grant Law has offices in Dallas, Fort Worth, Allen, Denton, Waco, and Rockwall. We have appeared in Dallas County courts for more than 30 years, across more than 500 trials to verdict.

Call (214) 225-7117 for a confidential consultation.