How do you prove a traumatic brain injury in court?

By Michael Shemtoub, trial attorney, Beverly Law. Updated November 2026.

What a jury has to find

In a California civil case, the side with the burden of proof must persuade the jury that what it has to prove “is more likely to be true than not true” (CACI No. 200). For an injured person, that means each part of the claim: the injury, its cause and the losses.

Causation is where most brain injury cases are fought. Under CACI No. 430, the defendant’s conduct must be a substantial factor in causing the harm, meaning “more than a remote or trivial factor.” It “does not have to be the only cause.” That matters when the defense points to an old concussion, depression or a stressful job. Texas and Washington juries receive their own instructions. In all three states, a doctor’s opinion is usually the bridge between the accident and the symptoms. Texas cases are handled by the firm’s Texas-licensed attorneys, Joyce Ondich and John Efstathiou.

Medical evidence, and what each test can and cannot show

Each test answers a narrow question, and a good case uses them for what they do well.

• Glasgow Coma Scale. Emergency staff score eye opening, speech and movement from 3 to 15. A clinical reference from the National Library of Medicine (StatPearls) notes that alcohol, drugs and sedatives can falsely lower the score and that the scale is a limited predictor of long-term outcome. A score of 15 in the ambulance does not settle the question.
• CT scan. According to NINDS, CT can show a skull fracture and brain bruising, bleeding or swelling.
• MRI. NINDS says MRI is more sensitive and “can pick up more subtle brain changes that a CT scan may miss.”
• Blood test. In 2018 the FDA authorized the first blood test to aid in evaluating adults with a suspected mild TBI (FDA). It measures two brain proteins, UCH-L1 and GFAP, in blood drawn within 12 hours of the suspected injury. The FDA’s decision summary says a negative result is associated with no acute lesions on a head CT, and the test is used with other clinical information to help decide whether a CT is needed.
• Thinking and memory tests. The CDC says providers may test learning, memory, concentration and problem solving, and that “even if the injury doesn’t show up on these tests, you may still have a mild TBI or concussion.”

NINDS adds that current imaging, blood tests and other measures “can’t always detect damage from mild, concussive injuries.” In court, that sentence answers the defense argument that a normal scan means nothing happened. Our California TBI guide explains how neuropsychological testing and validity measures are reviewed in litigation.

Witnesses who knew you before

Doctors see you for minutes at a time. A spouse, a coworker, a supervisor or a teacher sees you for hours. Jurors often give weight to plain, specific accounts from these people: the bookkeeper who now double-checks every entry, the parent who forgets a child’s pickup time, the friend who stopped joining group dinners because noise became too much. The most useful statements describe concrete changes with dates. Ask these people to write down what they noticed while it is fresh, and keep old performance reviews, school reports or messages that show how you functioned before.

The defense medical exam in each state

The defense will usually ask its own doctor or psychologist to examine you. This is a defense medical exam, and the examiner is hired by the other side. Each state sets different ground rules.

Be on time, answer honestly and do not exaggerate or minimize. Tell your lawyer afterward what tests were given and how long they took.

Records you can start keeping now

Keep a short daily log of headaches, dizziness, sleep, missed work and tasks that have become hard. Save every discharge paper and appointment summary. Tell each provider how the accident happened and when each symptom started, since records that tell the same story from the start are harder to attack. For symptoms to report after a crash, see our page on concussion or brain injury after a crash. If you have a worsening headache, repeated vomiting, slurred speech, weakness or a seizure, call 911 or go to an emergency room.

What this means for your case

Proof of a brain injury is built in layers, and the first layer is laid in the first days after the accident. Get evaluated, follow up when symptoms continue and let the people around you document what they see. Once the injury is proven, the next question is its value, covered in how much a brain injury case is worth. If you are unsure whether what you have counts as a brain injury, read is a concussion a traumatic brain injury, and find related questions in our injury FAQs.

Common questions

Related pages

Injury law FAQs

Important: This page is general information, not legal or medical advice, and reading it does not create an attorney-client relationship. Every case is different; talk to a lawyer about yours. Texas cases are handled by the firm’s Texas-licensed attorneys, Joyce Ondich and John Efstathiou. Last reviewed: November 7, 2026.