Intersection Crash: Triage, Blood, and Skid Math
At 2100 hours, two vehicles collide at a rural intersection. Vehicle A ran the stop sign. Driver A, a 41-year-old male, smells of alcohol, has slurred speech, admits to "three beers," has a bleeding six-inch laceration on his forearm, and complains of neck pain. Driver B, 29, has chest pain from the airbag and a probable fractured wrist; she is ambulatory. Vehicle A's passenger, an 8-year-old, is crying but has no visible injury and is walking around. EMS is 12 minutes out. The road is two-lane, unlit, with no shoulder, and traffic is passing at 45 mph. Vehicle A left 96 feet of skid marks on dry asphalt; you estimate a drag factor of 0.70.
1. Set your priorities for the first twelve minutes, and explain how the DWI investigation fits around them without compromising patient care or the case.
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Order of operations:
- Scene safety. Position the patrol car to block, activate emergency lighting, and get traffic control started. A rescuer struck by a passing car helps no one. Request a second unit for traffic.
- Triage. Driver A's forearm laceration is bleeding but not spurting - steady venous bleeding responds to direct pressure and a pressure dressing; a tourniquet is for life-threatening extremity hemorrhage, not this. He also has neck pain and should not be moved except for an immediate danger; hold c-spine and let EMS package him. Driver B's chest pain after an airbag deployment is potentially serious - she gets monitored, seated, and not walked around. The 8-year-old gets assessed, kept warm, and kept within sight; a child who is walking is still a child who needs evaluation.
- Detain, do not interrogate. Driver A is not free to leave, but medical questions come first. "Where does it hurt, are you on any medication, did you hit your head" is not a Miranda problem; "how much did you have to drink" is a statement you should be prepared to account for.
- Start the DWI clock. Note the time of driving, the time of contact, and every observation as you make it. Odor, speech, balance, and admissions are perishable.
The mistake to avoid: delaying medical care to run sobriety tests in the roadway. You do not need field sobriety tests to establish probable cause when you have a crash, odor, slurred speech, and an admission - and you would lose both the patient and the case if he deteriorates while you administer the walk-and-turn.
2. The hospital is 20 minutes away. Driver A is injured. Analyze the implied consent question: breath, blood, or warrant - and what happens if he refuses?
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Probable cause first. Odor of alcohol, slurred speech, an admission of drinking, and a crash caused by running a stop sign, taken together, easily support probable cause for DWI (G.S. 20-138.1). Without probable cause, none of the testing options are available.
The three paths:
- Breath. If he consents, the Intoximeter at the jail or a mobile unit is the routine route. But he is injured and going to the hospital; the machine is not going to him.
- Blood under the injury provision. North Carolina's implied consent statute permits a blood draw without consent in specified circumstances, including crashes involving death or serious personal injury. Whether Driver A's injuries cross the statutory "serious personal injury" threshold is a judgment you should not make alone - clarify with your supervisor or DA before relying on it.
- Search warrant. This is usually the cleanest, most defensible path when there is time, and there is time here: the draw happens at the hospital, where he is going anyway. A warrant removes the entire consent argument from the hearing.
If he refuses:
- Complete the refusal documentation and advise him of the consequences, as the statute requires.
- A first willful refusal carries a one-year license revocation; a subsequent refusal within the statutory look-back period carries a substantially longer one.
- Refusal is admissible evidence at trial in North Carolina - but only if the statutory advisement and documentation are done correctly. Read the form aloud, do not paraphrase it, and do not editorialize.
- Do not tell him refusal will be painless or that a warrant is impossible. That is how a refusal advisement becomes a due process issue.
3. Estimate Vehicle A's minimum speed from the skid marks and identify at least two evidentiary limits on that number.
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Formula: S = √(30 × d × f), where d is skid distance in feet and f is the drag factor.
S = √(30 × 96 × 0.70) S = √(2016) S ≈ 45 mph
That is the speed at the start of the skid, not the speed at impact, and it is a minimum estimate of the speed the vehicle was carrying.
Limits on the number - say these out loud in your report and on the stand:
- Drag factor is an estimate. 0.70 is a judgment about the surface; wet, worn, or dirty asphalt, or a different tire compound, moves the answer. Document how you arrived at it and who measured the marks.
- Not all wheels may have been braking. The formula assumes all-wheel braking. If only the rear or front wheels locked, or if the vehicle yawed, the true speed is higher than the number produced.
- ABS. A vehicle with functioning anti-lock brakes may leave faint or no skid marks, so the absence of marks proves nothing about speed.
- Road grade and surface changes over the 96 feet are not captured by a single drag factor.
- Skid marks end where braking ends. The vehicle can be faster at impact than at the start of the mark only in unusual cases; ordinarily impact speed was lower. Be precise about which speed you are describing.
Use the number to corroborate the reconstruction, not to replace it. If the case is going to trial, this is the kind of calculation that belongs to a certified reconstructionist, not to a patrol estimate.