Biomarker Evidence in TBI Litigation

Up to 90% of mild TBIs are missed on standard CT imaging. Defense counsel routinely uses “normal scans” to argue there is no injury at all — or that any symptoms are pre-existing, psychosomatic, or exaggerated.

Biomarkers like GFAP and NfL are released into the bloodstream in response to specific types of neural damage. A positive result is not subjective, not patient-reported, and not dependent on imaging resolution. It is a direct biochemical signal of injury.

GFAP and UCH-L1 have received FDA clearance for the evaluation of mild TBI. That clearance, combined with extensive peer-reviewed validation, satisfies the standard reliability factors courts apply: testing, peer review, known error rate, general acceptance.

The 2025 Mendez v. Koozies trial in Bexar County admitted a full biomarker panel — GFAP, NfL, and p-Tau 217 — without a contested Daubert ruling. That practical precedent has reassured plaintiffs’ firms that properly grounded biomarker testimony will hold up.

Carriers settle on perceived trial risk. When the only evidence of injury is symptom report plus a normal scan, exposure is bounded. When biomarker results corroborate the clinical picture, the analysis shifts: causation becomes harder to attack, damages become easier to model, and the settlement curve moves up.

Firms reporting biomarker use in TBI matters consistently describe larger demands, faster movement, and a willingness from defense to engage on damages rather than litigate injury existence.

Expect three lines of attack: (1) timing — that the draw was outside the validated window; (2) confounders — that another condition could elevate the marker; (3) clinical irrelevance — that a positive marker does not equal disabling injury.

Each is answerable with documentation: a draw timestamp inside the labeled window, a thorough medical history, and expert testimony that ties marker levels to clinical findings and functional impairment.

Biomarker evidence is only as strong as the record behind it. Best practice: draw within the validated window, document the exact time of injury and time of draw, use an accredited lab, and preserve every chain-of-custody record from collection through reporting.

Pair the lab result with contemporaneous clinical notes, imaging reports, and neurocognitive testing. The biomarker is the anchor; the surrounding record is what carries it through cross-examination.

Order early. The diagnostic window for acute markers like GFAP is hours to days, not weeks. In any case involving a head strike, loss of consciousness, persistent post-concussive symptoms, or contested causation, a baseline biomarker draw should be on the intake checklist.

For chronic or longitudinal cases, NfL provides a trajectory marker that can document ongoing axonal injury months after the event.