Hoy Law Wins Supreme Court Decision Establishing Federal Trucking Regulations as the Standard of Care in South Dakota
On February 4, 2026, the South Dakota Supreme Court issued a landmark decision in Hamer v. Duffy, 2026 S.D. 4, that fundamentally changes how truck accident cases are tried in this state. Hoy Law of Sioux Falls represented Justin and Kim Hamer throughout this years-long fight, from trial through oral arguments before the Supreme Court, and secured a ruling that establishes federal trucking safety regulations as the legal standard of care for commercial truck drivers in South Dakota.
The decision reversed multiple trial court errors, confirmed that violations of the Federal Motor Carrier Safety Regulations (FMCSRs) can constitute negligence per se under state law, reinstated critical expert testimony, and remanded the case for a new trial. The unanimous opinion was joined by Chief Justice Jensen and Justices Salter, Myren, and retired Justice Kern.
The Accident
On April 9, 2019, Justin Hamer was driving west on 271st Street near the Interstate 29 interchange in Lincoln County when he approached a malfunctioning traffic signal flashing red in all directions. Hamer stopped at the light and proceeded into the intersection. At the same time, Paul Duffy, who was operating a commercial truck for his employer Cornerstone Poured Foundations, entered from the opposite direction, turned left toward the I-29 on-ramp, and struck Hamer’s pickup.
With no independent witnesses and both drivers claiming the right of way, the responding officer issued no citations. Hamer suffered injuries and sought damages for medical expenses, lost earning capacity, pain and suffering, and property damage. His wife Kim filed an accompanying claim for loss of consortium.
A Case Gutted Before It Reached the Jury
What should have been a case decided on its full merits was severely restricted by a series of pretrial rulings that stacked the deck against the Hamers.
The trial court excluded testimony from both of Hamer’s expert witnesses, Adam Grill, a commercial vehicle safety expert, and Michael DiTallo, an accident reconstructionist, ruling their testimony would not be helpful to the jury. The court also denied Hamer’s motion to amend his complaint to include violations of the FMCSRs and refused to instruct the jury on those federal safety standards.
Without expert testimony or federal safety regulations in play, the jury found both drivers negligent but concluded Hamer’s negligence was “more than slight,” awarding him zero damages under South Dakota’s contributory negligence standard.
Hoy Law refused to let that be the final word.
The Supreme Court Reversal
On appeal, the South Dakota Supreme Court agreed with Hoy Law on three critical issues, reversing the trial court and remanding the case for a new trial.
Federal Trucking Regulations Set the Standard of Care
In what may be the most significant aspect of this decision, the Supreme Court ruled that the FMCSRs, which South Dakota’s Legislature adopted into state law under SDCL 49-28A-3, can establish the standard of care for commercial truck drivers. The Court held that an unexcused violation of these safety regulations may constitute negligence per se, just like any other traffic safety statute.
The defense had argued, and the trial court agreed, that the FMCSRs do not create a “private cause of action” and therefore could not be used in a state negligence case. The Supreme Court rejected that reasoning. Drawing on its longstanding rule that an unexcused violation of a statute enacted to promote safety constitutes negligence per se, the Court concluded that this principle applies equally to the FMCSRs that South Dakota adopted into its own laws.
The Court drew a clear distinction between the FMCSRs and other federal statutes, like the National Flood Insurance Act at issue in its earlier Highmark decision, that were enacted for financial rather than safety purposes. The FMCSRs, the Court noted, were enacted specifically “to promote the safe operation of commercial motor vehicles” and to ensure compliance with traffic safety laws. Because the Legislature adopted these safety-focused regulations, they carry the same weight as any other state safety statute.
Expert Witnesses Were Wrongly Excluded
The Supreme Court also found that the trial court abused its discretion in excluding both of Hamer’s expert witnesses.
Adam Grill, a commercial vehicle safety expert, was prepared to testify about the heightened performance standards, training requirements, and federal regulations specific to CDL holders operating commercial motor vehicles. His testimony would have helped the jury understand that driving a large commercial truck demands specialized skills far beyond those of an ordinary motorist, including differences in maneuverability, stopping distance, acceleration, and the broader set of regulations CMV drivers must obey. The Court found this testimony clearly met the standard for admissibility under Rule 702, as it provided technical and specialized knowledge that laypersons who have never driven such vehicles would not have.
Grill’s testimony was also directly relevant to the fatigue issue. At trial, Duffy admitted he worked 13-hour days and slept only six and a half hours in broken overnight shifts. He would go to bed at 8:30 p.m., wake at 11:30 p.m. to deliver papers until 2:30 a.m., then sleep again until 6:00 a.m. Grill would have testified that federal regulations require at least eight hours of off-duty rest before operating a commercial vehicle.
Michael DiTallo, an accident reconstructionist, had calculated that Duffy had between 4.4 and 4.9 seconds to perceive and react to Hamer’s approaching vehicle, which was more than enough time to avoid the collision. He also opined that Duffy was situationally inattentive and failed to yield to an approaching vehicle while making a left turn. The Court noted that no accident reconstruction was performed at the scene, making DiTallo’s analysis all the more valuable to the jury.
In a particularly striking detail, the Court pointed out that after successfully blocking DiTallo’s testimony, defense counsel turned around and argued these very same points to the jury in closing, telling them to think about distance, speed, and which vehicle likely accelerated faster, while conceding “I’m not here to tell you that I’m solving this case.” The Supreme Court recognized this for what it was: the defense used the absence of expert testimony to its advantage on the exact issues that testimony would have addressed.
The Court concluded there was a reasonable probability the jury would have reached a different outcome had both experts been allowed to testify, making the exclusion prejudicial error.
The Jury Should Have Been Instructed on 49 C.F.R. § 392.3
Federal regulation 49 C.F.R. § 392.3 prohibits operating a commercial motor vehicle while the driver’s ability or alertness is impaired by fatigue, illness, or any other cause. Hamer’s original complaint alleged that Duffy failed to “stay vigilant, awake, and alert,” which directly tracks the language of this regulation. The Supreme Court ruled that the trial court abused its discretion in refusing to instruct the jury on this regulation as the applicable standard of care.
What This Means for Truck Accident Cases in South Dakota
This decision has practical consequences that extend well beyond the Hamer case.
Negligence Per Se Changes the Game at Trial
Under ordinary negligence, a plaintiff must prove that the defendant failed to act as a reasonably careful person would under the circumstances. That standard invites debate, and defense attorneys can argue all day about what a “reasonable” truck driver would have done. Negligence per se eliminates that debate. If a truck driver violated a specific safety regulation and that violation caused the injury, the driver is negligent as a matter of law. The jury does not need to decide whether the driver was being “careful enough.” The regulation itself defines the minimum standard, and falling below it is negligence.
A Broad Range of Regulations Now Apply
The FMCSRs adopted by South Dakota under SDCL 49-28A-3 cover far more than just the fatigue rule at issue in Hamer. They include regulations governing driver fatigue and hours of service, safe driving in hazardous conditions such as snow, ice, fog, and rain, vehicle inspection, repair, and maintenance, driver qualifications and CDL requirements, and the general obligation to operate commercial vehicles in compliance with all applicable laws. Any of these regulations could form the basis of a negligence per se claim when a violation leads to injury.
Settlement Leverage Before Trial
Perhaps the most immediate practical impact is on settlement negotiations. When a plaintiff can point to a specific federal safety regulation the truck driver violated, backed by the Supreme Court’s confirmation that such violations constitute negligence per se, the calculus changes significantly for the defense. The question shifts from “can we convince a jury this driver was reasonable?” to “how do we defend against a regulation the driver clearly broke?” That is a much harder position to negotiate from, and it gives truck accident victims meaningful leverage well before a case ever reaches a courtroom.
Trucking Companies Are on Notice
This ruling does not just affect individual drivers. Under the doctrine of respondeat superior, employers are liable for the negligent acts of employees acting within the scope of their employment. When a truck driver violates the FMCSRs and causes an accident while on the job, the trucking company that put that driver on the road can be held accountable. The Hamer decision sends a clear message to every company operating commercial trucks in South Dakota: the federal safety regulations your drivers are required to follow are not suggestions. They are the legal standard of care, and violating them has real consequences.
The Fight Continues
For the Hamers, this Supreme Court victory means a new trial where their full case, including expert testimony and federal safety regulations, can finally be presented to a jury. For every other South Dakotan who shares the road with commercial trucks, the law is now clearer and stronger.
Hoy Law represented Justin and Kim Hamer before the South Dakota Supreme Court and secured this landmark ruling. If you or a loved one has been injured in a truck accident in South Dakota, contact our South Dakota truck accident lawyers to discuss how this decision may strengthen your case.
