DOT Shoulder-Maintenance Standards as Discretionary Functions: Sovereign Immunity Bars Individual-Capacity Negligence Claims

Introduction

Estate of Sanborn v. Peterson, 2026 S.D. 14, arises from a fatal two-vehicle collision on U.S. Highway 281 near Bonilla, South Dakota, in which Kylee L. Sanborn and Jayna R. Sanborn died after their vehicle left the paved surface and attempted to re-enter from a gravel shoulder alleged to be several inches below the pavement.

The plaintiffs (the Estates, through personal representative Sarah C. Sanborn) sued six South Dakota Department of Transportation (DOT) employees—Mark Peterson, Todd Hertel, Brad Letcher, Dan Martel, Michael Hieb, and Terence Peck—in both their official and individual capacities. The theory was negligence: the employees allegedly failed to maintain and repair the highway shoulder “flush” with the pavement in compliance with statutes, DOT maintenance policies, and federal/AASHTO guidance.

The core appellate issues were doctrinal rather than factual: (1) whether sovereign immunity barred claims against DOT employees in their individual capacities because the acts at issue were discretionary, and (2) whether the public duty doctrine independently barred the claims. The Supreme Court affirmed summary judgment for defendants on the individual-capacity claims, but on sovereign immunity grounds, and did not reach the public duty doctrine.

Summary of the Opinion

The Court held that none of the sources invoked by the plaintiff—federal and state highway maintenance statutes, AASHTO “control documents” (including the “Green Book”), DOT Policy Number OM-2002-09, Performance Standard Function 2158, or alleged inspection practices—created the kind of ministerial duty required to overcome sovereign immunity. Instead, the DOT employees’ alleged conduct involved discretionary functions, particularly because Performance Standard Function 2158 expressly authorizes modification or deviation based on “experience and judgment,” weather, roadway conditions, and priorities, and uses recommendatory language (“should”).

As a result, sovereign immunity barred the individual-capacity negligence claims, and summary judgment for defendants was affirmed (on a different rationale than the circuit court’s reliance on the public duty doctrine).

Analysis

Precedents Cited

1) Constitutional and structural foundations of sovereign immunity

  • The Federalist No. 81 (Alexander Hamilton) and Hans v. Louisiana, 134 U.S. 1 (1890): the Court invoked these authorities to situate sovereign immunity as an attribute of sovereignty—suit is permitted only by consent. These citations frame the opinion’s insistence that waiver is legislative, not judicial.
  • LP6 Claimants, LLC v. S.D. Dep't of Tourism & State Dev., 2020 S.D. 38, and Bickner v. Raymond Twp., 2008 S.D. 27: used to restate South Dakota’s rule that sovereign immunity bars tort liability unless the Legislature expressly waives it, and that waiver is construed narrowly.

2) The discretionary/ministerial divide for state employees

  • King v. Landguth, 2007 S.D. 2, Wulf v. Senst, 2003 S.D. 105, and Kyllo v. Panzer, 535 N.W.2d 896 (S.D. 1995): these cases supply the governing framework: employees share the State’s immunity when performing discretionary functions, but not when performing ministerial functions.
  • Ritter v. Johnson, 465 N.W.2d 196, and Nat'l Bank of S.D. v. Leir, 325 N.W.2d 845 (S.D. 1982): cited to explain the theory behind employee immunity—discretionary acts participate in sovereign policy-making power; ministerial acts execute established policy without undermining sovereignty.

3) Modern articulation of “ministerial” and its strictness

  • McGee v. Spencer Quarries, Inc., 2023 S.D. 66, and Truman v. Griese, 2009 S.D. 8: these are the opinion’s principal tools. The Court quoted the stringent definition of “ministerial” (absolute, certain, imperative; time/mode/occasion prescribed so nothing remains for judgment). McGee also supplies the key nuance: although “highway repair is generally considered to be ministerial in nature,” repair and maintenance become discretionary when they involve planning, policy decisions, or “actions that are not subject to an established standard.”
  • Swanson v. United States, 229 F. Supp. 217 (N.D. Cal. 1964): used to acknowledge that most governmental action involves some discretion, reinforcing the Court’s skepticism of broad attempts to recharacterize complex operational decisions as “ministerial.”

4) Highway-specific immunity and the “individualized inquiry”

  • Hansen v. S.D. Dep't of Transp., 1998 S.D. 109: cited for the proposition that discretionary vs. ministerial depends on “the facts of each particular case.” It also plays a prominent role in footnote 1, where the majority treated Hansen v. South Dakota Department of Transportation as foreclosing reliance on SDCL 31-32-10 as a ministerial-duty statute (a point Chief Justice Jensen questioned in his special concurrence).
  • Adrian v. Vonk, 2011 S.D. 84: cited for the concept that ministerial duties require “hard and fast rules” guiding the government’s actions.
  • Marson v. Thomason, 438 S.W.3d 292 (Ky. 2014): cited approvingly (as in McGee) to distinguish higher-level discretionary direction from ministerial execution.

5) Stare decisis and constraints on revisiting precedent

  • Earll v. Farmers Mutual Ins., 2025 S.D. 20, and In re Noem, 2024 S.D. 11: invoked to emphasize that prior holdings bind the Court absent extraordinary reasons to depart—used in support of the majority’s treatment of Hansen v. South Dakota Department of Transportation.

6) Procedure and standard of review backdrop

  • Healy Ranch, Inc. v. Healy, 2022 S.D. 43, Est. of Stoebner v. Huether, 2019 S.D. 58, Weiland v. Bumann, 2025 S.D. 9, and Barr v. Cole, 2023 S.D. 60: these cases provide the de novo review standard for summary judgment and reinforce the “entitled to judgment as a matter of law” framing of the immunity question.

Legal Reasoning

1) The Court’s sequencing: immunity first, merits later

The Court treated sovereign immunity not as a defense to be weighed against negligence facts, but as a threshold limitation on whether a plaintiff may sue government employees at all. This approach follows the opinion’s emphasis (via LP6 Claimants, LLC v. S.D. Dep't of Tourism & State Dev.) that waiver is legislative and limited.

2) Why the statutes did not create ministerial duties

The plaintiff relied on 23 U.S.C. § 116(b), SDCL 31-5-1, and SDCL 31-2-21, which use mandatory language (“shall”) regarding maintenance, repair, and DOT supervision.

The Court held these provisions allocate responsibility but do not prescribe how to perform each constituent maintenance act with the “absolute, certain, and imperative” specificity required by McGee v. Spencer Quarries, Inc. and Truman v. Griese. In other words: a mandatory assignment of duties to an agency is not the same thing as a ministerial command that removes judgment from day-to-day operations.

3) Why the federal/AASHTO “control documents” did not create ministerial duties

The “Green Book” language—“should be constructed and maintained flush”—and The Roadside Design Guide guidance—drop-offs “should not be left overnight” and “mitigating measures should be considered”—were treated as aspirational or conditional guidance rather than enforceable mandates that eliminate discretion. The Court emphasized the operational reality embedded in the documents themselves: they contemplate judgment, selection among options, and context-dependent mitigation.

4) The critical text: Performance Standard Function 2158

The opinion’s decisive move was textual. While DOT Policy Number OM-2002-09 states gravel shoulders “shall” be maintained in design condition, it does so “using the applicable standards for the work being performed.” For gravel shoulders, that standard is Performance Standard Function 2158, which:

  • labels itself a “guideline,”
  • expressly states the supervisor “shall retain the authority to modify or deviate … within their discretion,” and
  • uses “should” repeatedly for repair triggers and scheduling (including “seasonal conditions or other priorities”).

From this, the Court concluded that the “flush shoulder” concept was not an operational command with a compulsory result at a defined time and in a defined manner. Instead, the policy structure embeds managerial discretion about when to repair, how to prioritize, and whether to deviate.

5) The opinion’s didactic hypotheticals: Regulation A vs. Regulation B

The Court used two fence-painting hypotheticals to illustrate a consistent theme: even if a policy expresses a desired outcome, it is not “ministerial” unless it fixes the time/mode/occasion so that “nothing remains for judgment or discretion.” This framing aligned the DOT’s shoulder standards with the “Regulation A” scenario (judgment-laden triggers and undefined scheduling), not the “Regulation B” scenario (calendar-defined inspections and immediate repainting upon any exposed wood).

6) Inspection duties: discretionary absent clear standards

The plaintiff attempted to create a “readily ascertainable standard” through testimony that roads “should” be inspected weekly. The Court rejected this, characterizing it as the “quintessential discretionary act” because it was a unilateral professional judgment in the absence of a binding written frequency requirement—an analysis the Court anchored directly in Wulf v. Senst (no clear standards on when/how often to inspect; therefore discretionary).

7) Procedural consequence: affirmance on alternate grounds

The circuit court had granted summary judgment on the individual-capacity claims under the public duty doctrine. The Supreme Court affirmed the judgment but on sovereign immunity grounds, making the public duty doctrine issue unnecessary to decide.

Impact

1) Elevated importance of “anti-ministerial” drafting signals

Estate of Sanborn v. Peterson underscores that internal agency standards will not defeat sovereign immunity if they contain discretion-preserving language (e.g., “guideline,” “should,” and explicit authority to “modify or deviate”). Future plaintiffs will likely focus on identifying provisions resembling Wulf v. Senst and McGee v. Spencer Quarries, Inc.: concrete directives with defined timing and conditions that leave “no judgment or uncertainty.”

2) Narrowing pathway for highway-maintenance negligence suits against employees

Although the Court acknowledged prior statements that “highway repair is generally considered to be ministerial in nature,” it emphasized that this is not dispositive and that highway maintenance can be discretionary when governed by flexible standards. Practically, claims predicated on prioritization, scheduling, resource allocation, and deviation authority are more likely to be characterized as discretionary and therefore immune.

3) Incentives for policy design and legislative action

Chief Justice Jensen’s special concurrence highlighted a public-facing tension: motorists may assume there are enforceable standards requiring prompt repair of dangerous shoulders, but such standards—if they exist only as discretionary guidelines—may not support tort liability. The concurrence places the responsibility on the Legislature to expand liability if desired, echoing the majority’s structural view of sovereign immunity as a legislative choice.

4) Continued uncertainty regarding SDCL 31-32-10

Footnote 1 treated Hansen v. South Dakota Department of Transportation as foreclosing reliance on SDCL 31-32-10 as a ministerial-duty source, but the special concurrence questioned whether Hansen truly decided the statute’s application to highway damage “endanger[ing] the safety of public travel.” This preserves future litigation space around SDCL 31-32-10’s scope, even as the majority applied stare decisis to avoid reopening it here.

Complex Concepts Simplified

  • Sovereign immunity: a default rule that you cannot sue the State (and sometimes its employees) for torts unless the Legislature clearly allows it.
  • Discretionary act: a government employee decision involving judgment, prioritization, or policy choices (e.g., when to schedule repairs, how to allocate crews). Discretionary acts are typically immune.
  • Ministerial act: a task the law or binding policy requires in a specific way at a specific time/condition—so the employee has no real choice about whether to do it. Ministerial acts can expose employees to suit.
  • “Shall” vs. “should”: “shall” often signals a mandatory command, but the Court stressed context. A statute can mandate responsibility (“DOT shall maintain roads”) without mandating the precise operational steps needed to make maintenance “ministerial.” “Should,” “guideline,” and explicit deviation authority strongly signal discretion.
  • Public duty doctrine: a separate doctrine (not decided here) that can bar claims by treating certain governmental duties (public safety functions) as owed to the public at large rather than to specific individuals.

Conclusion

Estate of Sanborn v. Peterson reinforces a strict approach to identifying ministerial duties sufficient to overcome sovereign immunity for state employees. Even where policies articulate safety goals (like maintaining flush shoulders) and provide objective repair thresholds, the presence of discretion-preserving language—particularly express authority to deviate and recommendation-based phrasing—can render the duty discretionary and immunized.

The decision’s broader significance is its insistence that accountability for dangerous roadway conditions, when not tied to a truly mandatory and specific operational rule, is primarily a matter of legislative waiver rather than judicial expansion of liability.