FMCSRs Adopted in SDCL 49-28A-3 Set the Standard of Care for CMV Drivers and Can Support Negligence Per Se

Case: Hamer v. Duffy, Cornerstone Poured Foundations, Inc.
Citation: 2026 S.D. 4
Court: Supreme Court of South Dakota
Date: February 4, 2026
Disposition: Affirmed in part; reversed in part; remanded

1. Introduction

This appeal arises from a 2019 intersection collision between plaintiff Justin Hamer and defendant Paul Duffy, who was driving a truck in the scope of employment for Cornerstone Poured Foundations, Inc. The traffic signal at the intersection was malfunctioning and flashing red in all directions, leaving the right-of-way and each driver’s comparative care as central factual disputes. Justin and Kim Hamer sued Duffy for negligence and Cornerstone under respondeat superior. Cornerstone denied negligence and asserted contributory negligence.

The case reached the Supreme Court of South Dakota after a jury found Duffy negligent but also found Hamer contributorily negligent “more than slight,” resulting in a zero-damages verdict. On appeal, Hamer challenged three pretrial/trial rulings: (1) denial of a late motion to amend to add direct-negligence claims against Cornerstone and to plead violations of the Federal Motor Carrier Safety Regulations (FMCSRs); (2) exclusion of two plaintiff experts (a CMV safety/standards expert and an accident reconstructionist); and (3) refusal to instruct the jury on 49 C.F.R. § 392.3 (fatigue/impairment).

The opinion is significant for clarifying how FMCSRs—specifically those adopted by the South Dakota Legislature in SDCL 49-28A-3— function in South Dakota tort litigation: they may supply the standard of care for commercial motor vehicle (CMV) drivers and may support negligence per se, notwithstanding that FMCSRs do not themselves create a freestanding private federal cause of action.

2. Summary of the Opinion

The Court issued a mixed ruling:

  • Amendment—direct negligence against employer: affirmed the denial as untimely and prejudicial where the proposed amendment substantially changed the theory of the case on the eve of trial by adding negligent entrustment/retention/supervision/training claims premised on numerous FMCSRs.
  • Amendment—FMCSR allegations as to Duffy’s negligence: reversed. Allegations that Duffy was subject to FMCSRs and violated 49 C.F.R. § 392.3 (fatigue impairment) did not introduce a new liability theory; they provided additional statutory/regulatory grounding for the already-pleaded negligence theory. Denying amendment on “prejudice” grounds was an abuse of discretion as to this narrower subset.
  • Futility rationale rejected: reversed the circuit court’s legal conclusion that FMCSRs were “futile” because they do not create a private cause of action. The Court held FMCSRs adopted in SDCL 49-28A-3 may establish a standard of care for common-law negligence claims against CMV drivers, and unexcused violations may constitute negligence per se.
  • Expert exclusion reversed: the circuit court abused discretion by excluding the testimony of Adam Grill (CMV standards/defensive driving) and Michael DiTallo (accident reconstruction), as both would help the jury determine comparative fault and causation; the exclusion was prejudicial.
  • Jury instruction reversed: refusing to instruct on 49 C.F.R. § 392.3 was an abuse of discretion because it stated applicable law and was supported by evidence (sleep/work schedule raising a fatigue issue).

The Court remanded for further proceedings consistent with these holdings.

3. Analysis

3.1 Precedents Cited

The Court’s analysis is anchored in three doctrinal clusters: (i) amendment of pleadings and prejudice; (ii) whether federal law/regulations can supply a duty/standard of care in state negligence claims; and (iii) admissibility of expert evidence and jury instructions.

A. Pleading amendments: prejudice, timing, and futility

  • Ries v. JM Custom Homes, LLC (2022 S.D. 52): The Court used Ries for the governing abuse-of-discretion standard and for the proposition that “the most important consideration” is prejudice to the nonmoving party, commonly shown by surprise and lack of preparation. This framing supported affirmance of the denial as to new direct-negligence claims against Cornerstone.
  • Prairie Lakes Health Care Sys., Inc. v. Wookey (1998 S.D. 99): Quoted for the inquiry into whether the nonmoving party had a fair opportunity to litigate the new issue and offer additional evidence. The Court applied this principle to conclude that last-minute direct-negligence theories would have shifted the case to Cornerstone’s historical hiring/training/supervision practices, likely requiring reopened discovery and new experts.
  • In re Wintersteen Revocable Tr. Agreement (2018 S.D. 12): Cited to confirm “futility” as a permissible reason to deny amendment—important because the circuit court relied heavily on futility (no “private cause of action” under FMCSRs), which the Supreme Court partially rejected as an error of law.
  • Bell v. Allstate Life Ins. Co. (8th Cir. 1998): Quoted for the caution that late amendments adding new theories with different factual/legal issues and additional discovery burdens are properly denied due to prejudice. The Court used this federal authority (and Wright & Miller treatise) as persuasive support for denying employer direct-negligence additions made after discovery had closed and trial was imminent.
  • Olson v. Huron Reg'l Med. Ctr., Inc. (2025 S.D. 34): Used for the proposition that an “error of law is never within the range of permissible choices” and thus is an abuse of discretion. This mattered because the circuit court’s futility analysis treated the lack of a private federal cause of action as barring use of FMCSRs in negligence—an incorrect legal premise under the Court’s analysis.

B. Federal statutes/regulations as state-law duties/standards

  • Highmark Fed. Credit Union v. Hunter (2012 S.D. 37): The defense invoked Highmark to argue that if federal law provides no private right of action, it cannot establish a duty/standard in a state negligence claim. The Court distinguished Highmark because the National Flood Insurance Act (NFIA) served financial/fiscal purposes and was not enacted primarily to protect borrowers, while the FMCSRs are safety regulations designed to promote safe CMV operation—and crucially, were adopted by South Dakota in SDCL 49-28A-3.
  • Hofbauer v. Northwestern Nat'l Bank of Rochester (8th Cir. 1983): Cited (including in footnote discussion) for the principle that whether federal statutes establish a standard of care in state-based claims is a state-law question, and that even absent a private federal cause of action, a state may treat federal standards as relevant to common-law negligence. This supported the Court’s move away from an overly broad reading of Highmark.
  • Levene v. Staples Oil Co. (D.S.D. 2023): Heavily relied upon as a recent, on-point application of South Dakota negligence-per-se doctrine to FMCSR provisions adopted in SDCL 49-28A. The Court used Levene to reinforce that adopted FMCSRs can supply a standard of care and that their unexcused violation may be negligence per se. The opinion in Hamer effectively validates and imports Levene’s reasoning into state supreme court precedent.
  • Thompson v. Summers (S.D. 1997): Cited for the core South Dakota rule: an unexcused violation of a statute enacted to promote safety constitutes negligence per se. This rule becomes the bridge connecting FMCSRs (as adopted safety rules) to negligence-per-se instructions and pleading.
  • Davies v. GPHC, LLC (2022 S.D. 55): Quoted (via Levene) for the structured negligence-per-se test: where a statute/regulation protects persons in the plaintiff’s position or prevents the type of accident, an unexplained violation renders the defendant negligent as a matter of law.
  • Schmidt v. Royer (1998 S.D. 5): The Court cited Schmidt as its own prior instance of treating an FMCSR (49 C.F.R. § 393.52 on braking) as applicable in a negligence case and allowing its use for impeachment. This undercut any suggestion that FMCSRs are categorically irrelevant in South Dakota negligence litigation.
  • Nicolay v. Stukel (2017 S.D. 45): Cited to restate the general negligence-per-se formulation: violation of a statute/ordinance enacted for protection constitutes negligence per se if it proximately causes harm to a protected person.
  • Fritz v. Howard Twp. (1997 S.D. 122): Cited as another illustration of negligence per se where South Dakota adopted uniform national standards (traffic control device standards). It reinforces the point: adoption of external safety standards into state law supports negligence per se when violated.
  • Persuasive authorities from other jurisdictions: NFI Interactive Logistics LLC v. Bruski (Ind. Ct. App.); Fortner v. Tecchio Trucking, Inc. (E.D. Tenn.); Ballinger v. Gustafson (D. Neb.); and distinguishing cases Drake v. Old Dominion Freight Line, Inc. (D. Kan.) and Leon v. FedEx Ground Pkg. Sys., Inc. (D.N.M.). The Court used these to show that while FMCSRs may not create a standalone private federal claim, they are commonly admissible as standards relevant to negligence or negligence per se where state law permits.
  • R.B.J. Apartments, Inc. v. Gate City Sav. & Loan Ass'n (N.D. 1982): Appears in the Highmark discussion as part of the “no private cause of action” reasoning in the NFIA setting. Hamer distances itself from importing that rationale into the FMCSR/traffic-safety context, particularly given South Dakota’s legislative adoption of the FMCSRs.

C. Expert testimony and relevance/helpfulness under Rule 702

  • Thompson v. Avera Queen of Peace Hosp. (2013 S.D. 8): Cited for the abuse-of-discretion standard when reviewing admissibility of expert testimony.
  • Daubert v. Merrell Dow Pharm., Inc. (1993): Used for the proposition that the Rule 702 “helpfulness” requirement is primarily a relevance inquiry—expert testimony that does not relate to an issue is not helpful. The Court applied this to correct the circuit court’s mistaken focus on whether experts were “necessary,” rather than whether their testimony would “help” the jury.
  • Black v. Div. of Crim. Investigation (2016 S.D. 82): Quoted for the idea that helpful expert testimony must offer more than what jurors can infer for themselves—yet the Court concluded the proposed CMV standards testimony and accident reconstruction calculations were beyond common inference for many jurors.
  • State v. Johnson (2015 S.D. 7): Cited for the concept that experts may “educate the factfinder about general principles,” so long as the testimony fits, is reliable, and the expert is qualified. This supported allowing generalized CMV defensive-driving and regulatory context testimony, even if some aspects overlap with “common sense.”
  • Abrams v. FedEx Ground Package Sys., Inc. (S.D. Ill. 2022): Cited as persuasive authority that experts may present relevant FMCSRs to assist juries in understanding the trucking industry standard of care.
  • Accident reconstruction admissibility (persuasive cases): South v. Nat'l R. R. Passenger Corp. (AMTRAK) (N.D. 1980); Blalock v. Claiborne (Tenn. Ct. App. 1989); Hughes v. Vestal (N.C. 1965). These reinforce that reaction time, stopping distance, and similar reconstruction topics are proper expert subjects.

D. Jury instructions and prejudicial error

  • Weiland v. Bumann (2025 S.D. 9): Used for two key standards: (i) denial of instructions reviewed for abuse of discretion; and (ii) evidentiary error is reversible only if prejudicial, i.e., a reasonable probability of a different result.
  • Overfield v. Am. Und'rs Life Ins. Co. (2000 S.D. 98): Cited for the requirement that instructions must be supported by competent evidence and set forth applicable law. The Court concluded 49 C.F.R. § 392.3 was applicable law (adopted in SDCL 49-28A-3) and supported by evidence of Duffy’s sleep/work schedule.

3.2 Legal Reasoning

A. A granular approach to amendment: separating “new theory” from “new legal support”

The Court did not treat the proposed amendment as an all-or-nothing package. It separated: (1) new direct-negligence claims against Cornerstone (new theory; new factual focus; additional discovery; prejudice), from (2) additional allegations tied to Duffy’s driving conduct and applicable safety regulations (same theory; minimal disruption; no demonstrated prejudice).

This is an important procedural lesson from the opinion: when a late amendment is partially prejudicial and partially clarificatory, a court should assess prejudice claim-by-claim rather than deny wholesale—especially where the latter portion merely adds statutory/regulatory grounding to an already-pleaded negligence theory.

B. FMCSRs as state-law standard of care: adoption matters

The circuit court’s futility ruling assumed: “no private federal cause of action” → “cannot plead/use FMCSRs.” The Supreme Court rejected that equivalence for FMCSRs in South Dakota, emphasizing two points:

  1. State law controls duty/standard-of-care incorporation: The Court reiterated that whether federal statutes establish a standard of care in state claims is a matter of state law (Highmark Fed. Credit Union v. Hunter, citing Hofbauer v. Northwestern Nat'l Bank of Rochester).
  2. Legislative adoption and safety purpose: Unlike the NFIA in Highmark, the FMCSRs are safety regulations and—critically—were adopted by the South Dakota Legislature in SDCL 49-28A-3. Once adopted, they operate like other traffic safety statutes/regulations for negligence-per-se purposes.

The Court thus announced (and applied) a practical rule: FMCSRs adopted in SDCL 49-28A-3 may define the standard of care for CMV drivers in common-law negligence actions, and an unexcused violation may constitute negligence per se.

C. Expert testimony: “helpfulness” is not “necessity,” especially in comparative fault cases

The circuit court excluded both experts on the theory their testimony was not outside a jury’s common sense and not necessary to decide who had the right of way. The Supreme Court reframed the issues:

  • The case turned on comparative negligence, not merely right-of-way: Even if a jury can understand basic right-of-way rules, assigning relative degrees of fault in a flashing-red intersection collision implicates perception-response timing, defensive driving expectations, and CMV-specific operational realities.
  • CMV operations and professional standards can be specialized: Grill’s testimony was offered to explain how CMVs are more complex (maneuverability, stopping, acceleration, mass, licensing, regulatory obligations) and why professional drivers’ performance expectations differ even under the same overarching “ordinary care” standard.
  • Accident reconstruction provides technical assistance: DiTallo’s reaction-time and avoidance-time calculations (4.4 to 4.9 seconds) were precisely the type of expert assistance jurors generally cannot reliably derive unaided from raw facts, particularly where there was no reconstruction performed at the scene.

The Court also found prejudice: because the jury found both drivers negligent but barred recovery due to Hamer’s “more than slight” negligence, expert testimony could have materially affected the comparative negligence allocation—i.e., whether Hamer’s negligence was slight enough to permit damages.

D. Instruction on 49 C.F.R. § 392.3: aligning the jury charge with adopted safety law

The Court held the requested instruction on 49 C.F.R. § 392.3 should have been given because: (1) it was applicable law (adopted by SDCL 49-28A-3); (2) it fit pleaded theories (failure to stay vigilant, awake, and alert); (3) it was supported by evidence (Duffy’s sleep schedule and long workdays); and (4) the instruction properly treated violation as negligence (in line with South Dakota negligence-per-se doctrine for safety enactments).

3.3 Impact

A. Substantive tort impact: FMCSRs become a clearer negligence-per-se pathway in South Dakota CMV litigation

By holding that FMCSRs adopted in SDCL 49-28A-3 may supply the standard of care and support negligence per se, the Court strengthens plaintiffs’ and defendants’ ability to litigate CMV collisions through concrete regulatory benchmarks. This affects:

  • Pleading strategy: Parties can more confidently plead adopted FMCSR provisions as part of ordinary negligence or negligence per se theories against CMV drivers.
  • Instruction practice: Trial courts should expect requests for negligence-per-se instructions based on specific adopted FMCSRs (e.g., fatigue impairment under § 392.3), where evidence supports the violation and causation.
  • Proof and rebuttal: Regulatory content—training manuals, CDL standards, and FMCSR provisions—will more often become central evidence regarding breach and causation.

B. Procedural impact: more disciplined, claim-specific amendment analysis

The Court’s split amendment ruling encourages trial courts to parse proposed amendments and separately evaluate prejudice and necessity of additional discovery. Late additions that add entirely new theories against new targets (e.g., employer direct negligence) remain vulnerable; late additions that simply bolster existing negligence theories with adopted safety regulations are more likely to be allowed.

C. Evidentiary impact: a more permissive stance toward CMV and accident reconstruction experts

The decision underscores that “helpfulness” under SDCL 19-19-702 is not confined to rarefied scientific matters. In CMV cases, juror unfamiliarity with: (i) CMV operational constraints, (ii) professional driver expectations, (iii) perception-response timing, makes expert testimony especially relevant to comparative fault—often the dispositive issue in South Dakota’s fault allocation framework.

4. Complex Concepts Simplified

Respondeat superior

A doctrine making an employer liable for an employee’s negligence when the employee acts within the scope of employment. Here, Cornerstone admitted Duffy was acting in the course and scope, so vicarious liability depended on Duffy’s negligence.

Direct negligence claims against an employer (negligent entrustment/retention/supervision/training)

Unlike respondeat superior (derivative liability), these claims assert the employer itself acted negligently (e.g., hiring an unfit driver, failing to train, failing to supervise). They often require extensive discovery into company policies, prior incidents, hiring files, and compliance programs—one reason the Court found late pleading of such claims prejudicial.

FMCSRs and “private cause of action”

“No private cause of action” means you cannot sue solely because a federal regulation was violated, as a standalone federal claim. But a regulation can still matter in a state negligence case if state law adopts it or treats it as evidence of the standard of care. This opinion holds that, because South Dakota adopted key FMCSRs in SDCL 49-28A-3, they can function like state safety rules in negligence analysis.

Negligence per se

A doctrine where violating a safety statute/regulation (without a valid excuse) is considered negligence as a matter of law, leaving the jury to decide causation and damages (and often comparative fault). The Court treats adopted FMCSRs as capable of supporting negligence per se, similar to other traffic safety enactments.

“More than slight” contributory negligence (South Dakota comparative negligence framework)

The jury found Duffy negligent, but also found Hamer’s negligence was “more than slight,” which barred recovery under South Dakota’s comparative negligence regime as applied in this case. Because the entire verdict turned on fault allocation, evidence affecting comparative negligence—such as fatigue impairment standards and reaction-time calculations—was highly consequential.

Rule 702 “helpfulness”

Under SDCL 19-19-702, the question is not whether jurors could decide without an expert, but whether the expert’s specialized knowledge would help them understand evidence or decide an issue (like comparative fault, perception-response timing, or CMV-specific driving expectations).

5. Conclusion

Hamer v. Duffy, Cornerstone Poured Foundations, Inc. establishes an important South Dakota clarification: FMCSRs adopted by the Legislature in SDCL 49-28A-3 may supply the standard of care for CMV drivers, and unexcused violations may constitute negligence per se. The decision also corrects trial-level tendencies to treat expert testimony as “unnecessary” when it is, in fact, “helpful” to jurors tasked with allocating comparative fault, and it confirms that where evidence supports a fatigue/impairment theory, a jury should be instructed on 49 C.F.R. § 392.3.

At the same time, the Court preserves strong prejudice-based limits on late-stage pleading expansions that would substantially change the case—particularly direct-negligence claims against employers requiring new discovery and defenses. The combined effect is a more precise procedural framework and a more robust substantive role for adopted FMCSRs in South Dakota CMV negligence litigation.