Expert Testimony and Technical Construction Disputes in Contract and Tort:
Commentary on RTI, LLC v. Pro Engineering, Inc., 2025 S.D. 64

I. Introduction

RTI, LLC v. Pro Engineering, Inc., 2025 S.D. 64, is a significant South Dakota Supreme Court decision at the intersection of construction law, professional liability, and civil procedure. It addresses when expert testimony is required in disputes framed as breach of contract and breach of implied warranty, but which in substance challenge the technical adequacy of professional and specialized construction work.

The case arises from the design and construction of a highly specialized animal health research facility in Brookings, South Dakota. The facility was intended to meet USDA Biosafety Level 2 (BSL‑2) standards, with stringent requirements for air filtration, directional airflow, and pressure differentials designed to prevent cross-contamination between “clean” and “dirty” zones.

RTI, acting as its own general contractor, engaged:

• designArc Group, Inc. as architect;
• Pro Engineering, Inc. as mechanical/electrical/plumbing (MEP) engineer and HVAC designer;
• F.M. Acoustical Tile, Inc. (FM) to install suspended ceilings;
• Ekern Home Equipment Company to provide and install the HVAC and plumbing systems; and
• Trane U.S. Inc. as Ekern’s HVAC subcontractor and later as RTI’s service provider.

Following completion, RTI experienced serious operational failures: airflows ran in the wrong direction, the suspended ceiling moved and partially collapsed, and contamination allegedly ruined vaccine trials for a major client (Pacific GeneTec). RTI sued for breach of contract and breach of implied warranties. The circuit court, characterizing the claims as “professional negligence,” granted summary judgment to all defendants because RTI lacked qualified expert testimony and denied RTI’s motion to amend its complaint to add negligence and vicarious liability theories.

On appeal, the Supreme Court:

• Affirmed summary judgment for designArc, Pro Engineering, and FM due to the absence of expert testimony and the insufficiency of RTI’s CEO as an expert;
• Reversed summary judgment for Trane and Ekern, and
• Reversed the denial of RTI’s motion to amend, allowing RTI to pursue negligence against Trane and vicarious liability against Ekern.

The decision cements a key principle: in highly technical construction and design disputes, expert testimony may be required to prove breach and causation even when the claims are pled as contract or warranty, not negligence. At the same time, the Court reinforces limits on summary judgment procedure and clarifies the liberal standard for amending pleadings when no prejudice is shown.

II. Summary of the Opinion

A. Factual Background

RTI operates in the animal health research industry and set out to construct a BSL‑2 clinical research facility (the “Facility”) with individually ventilated animal rooms. The design called for:

• HEPA filtration of air entering and leaving test rooms;
• Air flowing from a “clean” corridor into animal rooms, then to a “dirty” corridor for exhaust;
• Negative pressure in animal rooms relative to the clean corridor to prevent contaminated air from escaping into clean areas; and
• Flexibility to adjust room pressures individually without extensive system rebalancing.

Shortly after completion (April 2016), several problems emerged:

• Inflexible pressure control: RTI discovered that adjusting pressure in a single room required rebalancing the entire HVAC system over 2–3 days.
• Need for room pressure monitors: RTI installed pressurization monitors (sensors) at a cost of about $35,000, after which air pressure controls functioned better.
• Ceiling movement and failure: Adjustments in room pressure caused the suspended (drop) ceiling to move up and down; wires allegedly snapped and portions of the ceiling collapsed, requiring replacement with hard ceilings in some rooms.
• Contamination of vaccine trials: During studies for Pacific GeneTec (PGT) regarding a poultry salmonella vaccine, RTI experienced contamination that required study repetition and eventually led to PGT terminating the contract.
• HVAC miswiring: A smoke test indicated air was flowing backward—from dirty to clean areas. RTI alleged, and Trane allegedly admitted, that Trane had wired the primary pressure controller backwards, reversing airflow direction. After rewiring, contamination stopped.

RTI alleged significant damages: costs to retrofit the HVAC and ceiling, uncompensated repeat studies, lost income from terminated or delayed projects, room downtime, and lost profits.

B. Claims Against Each Defendant

• designArc (Architect): Allegedly recommended or approved a suspended vinyl ceiling without coordinating with Pro Engineering to ensure it could withstand pressure changes; failed to specify appropriate ceiling products; this allegedly led to ceiling movement and collapse.
• Pro Engineering (Engineer/HVAC Designer): Allegedly failed to design an HVAC system that permitted room-by-room pressure adjustment without full rebalancing; did not specify needed equipment for precise adjustment; did not properly tie the clean corridor into the rest of the system; provided improper balancing instructions; and did not ensure clean corridor filtration and volume regulation.
• FM Acoustical (Ceiling Installer): Installed an all-aluminum suspended ceiling with gaskets. RTI alleged faulty installation (unconnected wires, unclipped tiles, gaps in perimeter framing) and contended this allowed air leakage and contributed to contamination and ceiling failure.
• Trane (HVAC Equipment Supplier/Installer): As Ekern’s subcontractor and later RTI’s service contractor, Trane allegedly wired the primary controller for the dirty corridor backwards, causing reversed airflow and contamination, and provided or installed equipment that did not operate properly or give accurate pressure readings.
• Ekern (HVAC/Plumbing Contractor): Contracted directly with RTI for HVAC and plumbing. RTI did not complain about plumbing but alleged Ekern bore responsibility for the HVAC work and was vicariously liable for Trane’s negligence as its subcontractor.

C. Circuit Court Proceedings

All defendants moved for summary judgment. The court:

• Viewed RTI’s claims as “professional negligence” regardless of the contractual or warranty labels;
• Held that expert testimony was required to establish the applicable standard of care, breach, and causation for each defendant’s role;
• Determined that RTI’s CEO, Rolland Nevins, was not qualified as an expert on architecture, engineering, or ceiling systems; and
• Granted summary judgment to all defendants on that basis.

RTI sought to amend its second amended complaint to add:

• A negligence claim against Trane (for defective performance of its subcontract with Ekern, on which RTI claimed third-party status), and
• A vicarious liability claim against Ekern for Trane’s negligence.

The circuit court denied the motion to amend as untimely (post-discovery and post-summary-judgment motions) and “futile” because the lack of expert testimony would persist even if negligence and vicarious liability were added.

D. Supreme Court’s Disposition

The Supreme Court decided three core issues:

1. Expert testimony and summary judgment:
   • Affirmed that expert testimony was required to prove RTI’s claims against designArc, Pro Engineering, and FM, and that Nevins was not a qualified expert for those technical issues.
   • Affirmed summary judgment for designArc, Pro Engineering, and FM.
   • Reversed summary judgment for Trane, holding that Trane had not moved for summary judgment on the “lack of expert” theory and that genuine issues of material fact existed about the alleged miswiring and system operation.
   • Reversed summary judgment for Ekern, because RTI had advanced a vicarious liability theory the circuit court never addressed.
2. Qualification of Nevins as an expert:
   • Held that the circuit court did not abuse its discretion in finding Nevins unqualified as an expert on architectural standards, engineering design, HVAC technicalities, or ceiling systems.
3. Motion to amend the complaint:
   • Held that RTI’s proposed negligence claim against Trane and vicarious liability claim against Ekern were not futile.
   • Found no demonstrated prejudice to Trane or Ekern from the late amendment, given their long-standing notice of the underlying factual allegations.
   • Concluded that the circuit court abused its discretion in denying leave to amend.

Thus, the case returns to the circuit court with claims against Trane (contract, warranty, and now negligence) and against Ekern (vicarious liability and possibly contract) to be litigated with an amended pleading.

III. Precedents and Authorities Shaping the Opinion

A. South Dakota Authorities

1. Expert testimony requirement

The Court builds on a line of South Dakota decisions requiring expert testimony when the subject matter is beyond lay understanding:

• Sheard v. Hattum, 2021 S.D. 55, 965 N.W.2d 134:
  In a general negligence context, the Court held expert testimony is required when the matter is not within the common knowledge or experience of laypersons (¶ 28).
• Luther v. City of Winner, 2004 S.D. 1, 674 N.W.2d 339:
  A plaintiff sued a city engineer for purportedly negligent sidewalk design. The Court held expert testimony is needed to establish the standard of care for a professional (such as an engineer) unless the issue lies within the common knowledge of the jury (¶ 9). The plaintiff’s failure to provide expert evidence was fatal to his professional negligence claim (¶¶ 11–12).
• Nemec v. Deering, 350 N.W.2d 53 (S.D. 1984):
  Addressing legal malpractice, the Court recognized that in some cases of alleged negligence or breach of contract, expert testimony is necessary to show that an attorney failed to meet the standard of reasonable professional care (p. 56). Nemec is important because it explicitly ties the expert requirement to both negligence and breach of contract claims in professional settings.
• Zhi Gang Zhang v. Rasmus, 2019 S.D. 46, 932 N.W.2d 153:
  Reaffirmed that when expert testimony is required and absent, the failure is fatal to the claim (¶ 41).

RTI leverages and extends these principles from classic malpractice into technical construction and design disputes, even where the claims are framed as contract and warranty.

2. Summary judgment standards

The Court reiterates its established summary judgment framework, citing:

• Estate of Olsen v. Agtegra Coop., 2024 S.D. 39, 9 N.W.3d 763:
  Summary judgment is proper only if there is no genuine issue of material fact and the movant is entitled to judgment as a matter of law, with all reasonable inferences drawn in favor of the non-moving party (¶ 12).
• Dahl v. Sittner, 429 N.W.2d 458 (S.D. 1988):
  Courts cannot grant summary judgment merely because they believe the non-movant is unlikely to prevail; issues must not be “sham, frivolous, or so unsubstantial” as to render litigation futile (p. 461).

In reversing summary judgment for Trane and Ekern, the Court emphasizes that disputed facts—such as whether Trane miswired the controller and whether Ekern may be vicariously liable—must be tried, not resolved via summary judgment on unbriefed theories.

3. Qualification of experts

On the question whether Nevins could serve as an expert, the Court relies on:

• People ex rel. O.S., 2005 S.D. 86, 701 N.W.2d 421:
  The trial court’s decision to qualify an expert witness is reviewed for abuse of discretion. An expert must have “special knowledge, skill, experience or training” to understand the matter about which he or she testifies (¶ 7).

The Court finds no abuse of discretion in excluding Nevins as an expert on architectural, engineering, HVAC, or ceiling design issues, given his own admissions about his lack of specialized training.

4. Amendment of pleadings

For the motion to amend, the Court applies South Dakota’s liberal amendment regime:

• SDCL 15‑6‑15(a): A pleading may be amended by leave of court, and “leave shall be freely given when justice so requires.”
• Isakson v. Parris, 526 N.W.2d 733 (S.D. 1995):
  Under SDCL 15‑6‑15(b), amendments should be allowed unless the opposing party is prejudiced—that is, unless the party lacked a fair opportunity to litigate the new issue or could have offered additional evidence if the case had been tried on that issue (p. 736).
• Kjerstad v. Ravellette Publications, Inc., 517 N.W.2d 419 (S.D. 1994):
  Denial of a motion to amend is reviewed for abuse of discretion; a motion should not be denied absent a clear abuse resulting in prejudice (p. 423).
• Noble for Drenker v. Shaver, 1998 S.D. 102, 583 N.W.2d 643:
  The Court approved amendment where the new theory had been effectively in play “from nearly the beginning” and defendants were not unfairly surprised or prejudiced (¶ 15).
• Fodness v. City of Sioux Falls, 2020 S.D. 43, 947 N.W.2d 619:
  Clarifies that abuse of discretion means a decision outside the reasonable range of choices, arbitrary or unreasonable (¶ 32).

RTI synthesizes these authorities to emphasize that lateness alone (post-discovery, post-summary-judgment motions) does not justify denying amendment where the defendants had long notice of the factual underpinnings and cannot show concrete prejudice.

B. Extra-Jurisdictional Authorities

The Court also draws on cases from other jurisdictions to illuminate the expert testimony requirement in technical contract and construction disputes:

• KOKO Development, LLC v. Phillips & Jordan, Inc., 101 F.4th 544 (8th Cir. 2024):
  Under North Dakota law, the Eighth Circuit held that both negligence and breach of contract claims in a land development dispute required expert testimony because the alleged breaches involved complex infrastructure and engineering issues beyond common knowledge (pp. 549–51).
  RTI cites KOKO as direct precedent for the principle that expert testimony can be essential in contract claims involving complex technical performance.
• Dan King Plumbing Heating & Air Conditioning, LLC v. Harrison, 869 S.E.2d 34 (N.C. Ct. App. 2022):
  The court acknowledged that some defective workmanship can be judged by laypersons, but where “substandard work” is not obvious and implicates professional standards of care, expert testimony is required to prove breach of a construction contract (esp. pp. 50, 52).
  The Court uses Dan King to illustrate the line between “obvious defects” that jurors can evaluate unaided and technical sufficiency issues requiring experts.
• Watson, Watson, Rutland/Architects, Inc. v. Montgomery County Board of Education, 559 So.2d 168 (Ala. 1990):
  A school district sued an architect for roof leaks. The Alabama Supreme Court held that expert testimony was necessary to prove whether the architect breached its contractual duty of inspection, because architectural standards and the nature of any breach were not matters of common knowledge (pp. 173–74).
  RTI relies on Watson to support the need for expert evidence in breach of contract claims against architects.
• Guy M. Cooper, Inc. v. East Penn School District, 903 A.2d 608 (Pa. Commw. Ct. 2006):
  Held that without expert testimony, a contractor’s evidence could not show that an architect failed to perform under its contract or fell below professional standards.
• Brooks Oil Service v. Rogers, No. LLICV095005394S, 2011 WL 6004377 (Conn. Super. Ct. Nov. 15, 2011):
  Observed that whether a licensed HVAC contractor defectively installed a system is beyond ordinary lay knowledge.
• Canale v. KBE Building Corp., No. UWYCV156026262S, 2017 WL 4621399 (Conn. Super. Ct. Sept. 5, 2017):
  Held that determining the proper installation, fastening, inspection, testing, and design of a ceiling falls outside the typical fact-finder’s experience and requires expert testimony (at *4).
• 17B C.J.S. Contracts § 1004:
  Explains that while some breaches are within common knowledge, expert testimony may be necessary when the breach goes to the “technical sufficiency” of performance, particularly in workmanlike-performance disputes.

These authorities reinforce the South Dakota Court’s view that technical sufficiency in specialized design and construction work cannot ordinarily be adjudicated without expert input.

IV. The Court’s Legal Reasoning

A. Contract vs. Negligence: Form vs. Substance

A central theme in the opinion is the Court’s willingness to look beyond the formal label of a claim (contract, implied warranty, negligence) to the underlying nature of the dispute. RTI’s pleadings used contract and implied warranty theories, but the factual gravamen was that the architect, engineer, and specialized contractors:

• Failed to design or specify systems adequate to meet RTI’s technical requirements; and
• Failed to perform construction/installation work in a technically competent manner.

The Court effectively treats these as professional or technical performance claims, regardless of doctrinal label. It then applies the rule that where the standard of performance and causation are beyond lay understanding, expert testimony is required—whether the claim is called negligence or breach of contract.

This is crystallized in ¶¶ 40–47:

• The Court notes that expert testimony is “often expressed” in negligence cases (e.g., professional malpractice), but “is not, however, limited to negligence actions; it can apply with equal force to a breach of contract claim” (¶ 42, citing Nemec and KOKO).
• It cites KOKO for the proposition that technical questions involving infrastructure and engineering are “similar” whether framed as negligence or breach of contract (¶ 44).
• It relies on Dan King and 17B C.J.S. to show that claims about technical sufficiency and workmanlike performance often need experts (¶¶ 45–46).

Accordingly, the Court holds that RTI’s claims against designArc, Pro Engineering, and FM require expert testimony “under either theory of recovery—negligence or breach of contract” (¶ 47).

B. Application to Each Defendant

1. designArc (Architect)

RTI alleged that designArc failed to:

• Determine ceiling specifications that could withstand anticipated pressure changes; or
• Coordinate with Pro Engineering or otherwise recommend ceiling products compliant with those requirements.

The alleged breach is essentially a failure to exercise professional architectural judgment in specifying structural components for a highly specialized BSL‑2 environment. The Court finds:

• These questions involve “the professional judgment of the architect and [are] not within the understanding of a nonprofessional witness” (¶ 48).
• Like in Watson, whether an architect’s design or inspection obligations were met is not a matter of common knowledge; expert testimony is required to establish the applicable standard of care and whether it was breached (¶ 50).

Because RTI offered no qualified architectural expert, it could not show either breach (what a competent architect should have done) or causation (whether any deviation caused the ceiling movement and collapse). Summary judgment for designArc was therefore appropriate (¶ 51).

2. Pro Engineering (Engineer and HVAC Designer)

RTI’s core complaint against Pro Engineering was that its HVAC design:

• Did not allow pressure adjustments in individual rooms without system-wide rebalancing;
• Did not properly tie the clean corridor into the rest of the system;
• Lacked suitable specifications for equipment to allow precise adjustment; and
• Failed to provide appropriate balancing instructions and volume regulation (¶¶ 13–15, 52–55).

These allegations concern:

• HVAC system architecture for a BSL‑2 facility;
• Coordination of airflows between clean, animal, and dirty zones; and
• Complex dynamic behavior of air pressure and flow under various operating conditions.

Relying on Luther, the Court notes that professional negligence claims against engineers require expert testimony unless the matter is within common knowledge—which is rarely the case in design disputes (¶ 53). The Court finds RTI’s claims against Pro Engineering to be “even more technical than the claims in Luther” (¶ 54).

The Court emphasizes:

• Laypersons may conceptually understand “direction of airflow,” but not the specialized design elements and equipment needed to achieve precise control under BSL‑2 constraints (¶¶ 54–55).
• Terms like “volume regulation” and system “balancing” are not self-explanatory to jurors, especially in a complex facility (¶ 54).
• The facility’s unique use—vaccine development with strict contamination controls—underscores the technical nature of the design obligations (¶ 55).

Without an engineering or HVAC expert, RTI could not prove Pro Engineering’s design deviated from professional standards or that such deviation caused the operational problems. Summary judgment for Pro Engineering is affirmed (¶ 55).

3. FM Acoustical (Ceiling Installer)

RTI’s case against FM focused on:

• Alleged deviations from the ceiling manufacturer’s installation instructions (unconnected wires, unclipped tiles, perimeter gaps); and
• The ceiling’s movement and partial collapse during pressure changes (¶¶ 16–18, 56–58).

Although FM was not involved in design, its installation work in this specialized facility had to meet particular performance requirements (e.g., airtightness, resistance to pressure differentials). The Court holds:

• Even “ordinary” construction defects may require expert testimony where the alleged deficiencies and their causal link to failure are not matters of common knowledge (¶ 56).
• For this BSL‑2 facility, determining whether the ceiling was correctly installed and whether any installation errors caused the movement and collapse is not within the typical juror’s experience (¶ 57).
• As in Canale, decisions about the correct installation, fastening, testing, and design of a ceiling system are technical issues requiring expert evidence (¶ 57).

Because RTI had no qualified ceiling or construction expert (and Nevins himself acknowledged that a “ceiling engineering expert” would be needed), its claims against FM could not survive summary judgment (¶¶ 56–58).

4. Trane (HVAC Subcontractor and Service Provider)

The procedural posture of Trane’s summary judgment motion is critical:

• Unlike the other defendants, Trane did not argue that expert testimony was required to defeat RTI’s contract and implied warranty claims.
• Instead, Trane argued:
  • It was not a party to RTI’s contract with Ekern;
  • RTI disavowed any direct contract claim against Trane; and
  • The products it supplied performed properly, with no evidence to the contrary (¶ 28).
• RTI, in turn, alleged that Trane had wired the primary controller “backwards,” reversing airflow and causing contamination and ceiling movement (¶¶ 20–22, 58–60).

The circuit court, however, granted summary judgment to Trane on the same “lack of expert” rationale used for the other defendants, even though Trane had not framed its motion that way (¶ 35). The Supreme Court reverses, for two reasons:

1. Procedural fairness and burden allocation:
   As the movant, Trane bore the burden to “clearly demonstrat[e] an absence of any genuine issue of material fact” (¶ 58, citing Estate of Olsen). It chose not to base its motion on the absence of expert testimony. The circuit court’s sua sponte application of that rationale—without giving RTI the chance to respond to that specific ground—was improper.
2. Existence of genuine factual disputes:
   RTI presented evidence, including deposition testimony and responses to Trane’s statement of undisputed facts, that:
   • Trane had admitted miswiring the controller (¶¶ 60–61 & n.5);
   • The miswiring caused reversed airflow and contamination; and
   • The system operation (drawing ceilings up and down, breaking wires, collapsing tiles) was linked to the behavior of the Trane-installed VAV components and controls (¶ 60).
   The Court concludes that, viewing the evidence in the light most favorable to RTI, these contested facts preclude summary judgment (¶ 61).

The Court explicitly leaves for remand the precise legal characterization of Trane’s alleged miswiring—as breach of contract, breach of implied warranty, negligence, or some combination—and emphasizes that these theories should be developed before the circuit court (¶ 61 n.8).

5. Ekern (Prime HVAC/Plumbing Contractor)

RTI did not allege that Ekern’s own plumbing or HVAC labor was defective; Nevins testified he was satisfied with Ekern’s work (¶ 23, 62). Instead, RTI’s theory (raised clearly in opposition to summary judgment) was that Ekern was vicariously liable for Trane’s negligence as Trane’s principal/prime contractor (¶¶ 23, 62).

The circuit court analyzed only a direct faulty-workmanship claim against Ekern and concluded that RTI needed expert testimony to support any allegations about Ekern’s own work (¶ 34, 62). It did not reach the vicarious liability theory at all. The Supreme Court holds:

• RTI advanced a distinct theory of liability—vicarious responsibility for Trane’s conduct—on which it was entitled to a legal determination (¶¶ 62–63).
• Because this theory was overlooked, summary judgment for Ekern was improper (¶ 63).
• This conclusion is reinforced by the Court’s decision to permit RTI to amend the complaint to expressly plead negligence against Trane and vicarious liability against Ekern (¶ 63).

The Court does not decide whether Ekern ultimately will be vicariously liable; it merely holds that RTI is entitled to litigate that theory (¶ 63).

C. Nevins’s (Lack of) Qualification as an Expert

RTI attempted to rely on its CEO, Rolland Nevins, as an expert witness in lieu of hiring independent architects, engineers, or construction specialists. RTI’s discovery disclosure indicated that Nevins “may have personalized knowledge and expertise within the role of CEO to testify as to Plaintiff’s monetary damages” (¶ 66). Yet RTI attempted to deploy him more broadly on:

• Standards of care for architects and engineers;
• Proper installation of suspended ceilings; and
• Causation issues regarding airflow, contamination, and ceiling collapse.

The Court affirms the circuit court’s decision that Nevins was not qualified to provide this kind of expert evidence. Key points include:

• Under People ex rel. O.S., an expert must have specialized knowledge, skill, experience, or training directly relevant to the subject matter (¶ 65).
• Nevins’s own testimony revealed:
  • He was not an architect, engineer, or HVAC installer;
  • He lacked formal engineering or installation experience;
  • He did not know whether the HVAC system contained the wrong equipment;
  • He acknowledged he lacked expertise regarding ceiling materials and their suitability for the facility; and
  • He admitted a specialized ceiling engineer would be needed to explain the cause of wire failure and collapse (¶¶ 68–69).
• While a business leader may competently testify about business damages (lost profits, etc.), that does not make him an expert in design and construction disciplines (¶¶ 66–69).

Given these admissions, the Court holds that the circuit court did not abuse its discretion in rejecting Nevins as an expert on technical design and construction issues (¶¶ 67–69). Without another qualified expert, RTI’s claims against designArc, Pro Engineering, and FM could not survive (¶ 70).

D. Amendment of the Complaint

RTI sought to file a third amended complaint adding:

• A “negligence” count against Trane based on its performance of contractual services owed to Ekern; and
• A vicarious liability claim against Ekern for Trane’s negligence (¶¶ 29–30, 71–73).

The circuit court denied the motion as:

• Untimely: filed 18 months after the deadline for amendments, after discovery closed, and after summary judgment motions were filed; and
• Futile: because, in the court’s view, RTI’s lack of expert testimony would continue to doom any negligence-based theory (¶ 72).

The Supreme Court reverses:

1. Futility:
   • Given the Court’s reversal of summary judgment for Trane and Ekern, negligence and vicarious liability are not futile theories (¶¶ 73–74).
   • There are triable factual disputes about Trane’s miswiring and contamination; negligence is therefore at least plausible.
2. Prejudice:
   • The decisive factor under SDCL 15‑6‑15 is whether the non-movants would be prejudiced—that is, deprived of a fair opportunity to litigate or to marshal additional evidence (¶¶ 71, 74–75).
   • Trane and Ekern had “known for some time” that Trane’s alleged negligence and Ekern’s vicarious liability were at issue (¶ 74). The amendment merely conformed formal pleadings to the legal theories already being argued.
   • No trial date had been set, and neither Trane nor Ekern demonstrated specific prejudice from the amendment (¶ 74–75).

The Court therefore holds that denying the motion to amend was “a fundamental error of judgment” outside the permissible range of choices, and thus an abuse of discretion (¶ 75).

V. Impact and Future Significance

A. Clarifying the Reach of the Expert Testimony Requirement

RTI solidifies a practical rule for South Dakota:

When a claim—whether styled as negligence, breach of contract, or breach of implied warranty—turns on the technical sufficiency of professional or specialized construction work, expert testimony will generally be required to establish both breach and causation unless the deficiency is obvious to laypersons.

This has several implications:

• Design and construction disputes: Claims against architects, engineers, HVAC designers, and specialized installers (e.g., ceiling, electrical, fire suppression) will often require expert testimony on industry standards and causal chains.
• Contract vs. tort framing: Litigants cannot avoid the expert requirement by choosing to plead only contract and implied warranty rather than negligence. Substance controls over form.
• Litigation strategy: Plaintiffs must budget early for expert retention and disclosure; relying on internal personnel as “experts” is risky unless those individuals genuinely possess appropriate professional credentials and experience.

B. Professional and Technical Performance in Contract Law

By explicitly citing Nemec and KOKO, the Court aligns South Dakota with jurisdictions recognizing that:

• Professional performance obligations can arise in both tort and contract; and
• Proof of a contractual breach grounded in technical or professional duties often requires the same kind of expert evidence as a tort-based malpractice claim.

Potential future ramifications include:

• Increased overlap between professional negligence and breach of contract doctrines, particularly concerning limitations periods, damages measures, and defenses;
• Greater emphasis on precise contractual allocation of design and performance responsibility, especially in design-build and construction-manager-at-risk settings; and
• Heightened importance of professional standard-of-care clauses in construction and design contracts.

C. Summary Judgment Practice: Limits on Sua Sponte Theories

The Court’s handling of Trane’s motion reinforces basic civil-procedure principles:

• Courts should not grant summary judgment on grounds the moving party did not raise, especially when those grounds turn on evidentiary issues like the need for expert testimony.
• Even in complex cases with multiple defendants, each motion must be evaluated on its own asserted bases and the specific record against that defendant.
• Factual disputes that go to the heart of the claim—such as whether Trane miswired the controller and whether that caused reversed airflow—are quintessential jury questions, not suitable for resolution on paper.

For practitioners, this underscores the need to track and respond to each defendant’s specific argument and the corresponding factual record. It also suggests that appellate courts will closely scrutinize trial courts that shortcut these requirements.

D. Liberal Approach to Amending Pleadings

The decision also reinforces South Dakota’s liberal policy favoring amendments:

• Even substantial shifts in legal theory (e.g., from contract/warranty to negligence and vicarious liability) may be allowed late in the case if they arise from the same core factual matrix and do not unfairly surprise or prejudice the opposing party.
• Expiration of the scheduling order’s amendment deadline and completion of discovery are relevant but not dispositive; the decisive factor is prejudice.
• Parties should expect that if an issue has been substantively litigated in motion practice or discovery (e.g., whether Trane miswired the system), the opposing party may be allowed to amend to formalize all plausible legal theories flowing from that factual premise.

E. Specialized Facilities and Construction Risk Allocation

Although the decision focuses on procedural and evidentiary issues, it indirectly highlights risks in highly specialized facilities, such as:

• Complex biosafety and HVAC requirements (e.g., BSL‑2, HEPA filtration, directional airflow);
• Integration among disciplines (architecture, engineering, HVAC, ceiling systems, controls); and
• High business-consequence failures (lost clients, terminated contracts, contamination of research studies).

Owners and contractors may react by:

• Increasing reliance on specialized consultants early in design;
• More clearly allocating responsibilities for systems performance (pressurization, filtration, contamination control) in contracts; and
• Crafting more precise performance standards and testing/commissioning protocols to document compliance or breach.

While the Court does not prescribe contractual best practices, the factual context of RTI is likely to drive more meticulous attention to system integration, especially in research, healthcare, and laboratory projects.

VI. Simplifying Key Legal and Technical Concepts

A. Professional Negligence vs. Ordinary Negligence vs. Breach of Contract

• Ordinary negligence is failure to use reasonable care that a typical person would use in similar circumstances.
• Professional negligence (malpractice) arises when a licensed or specialized professional (e.g., architect, engineer, doctor, lawyer) fails to meet the standard of care of reasonably careful professionals in that field.
• Breach of contract occurs when a party fails to perform duties promised in a contract. When those duties are professional or technical in nature, proving breach often requires showing that the performance fell below professional norms—hence the need for expert testimony.

In RTI, although RTI pled contract and warranty, the underlying allegations—that the architect and engineer designed flawed systems and the ceiling contractor installed work improperly—functionally amount to professional or technical negligence claims.

B. Expert Testimony and the “Common Knowledge” Exception

Expert testimony is required when jurors cannot reasonably evaluate the standard of care or causation based on common experience. The “common knowledge” exception allows lay jurors to decide obvious matters without experts—for example:

• A surgeon leaving a sponge inside a patient; or
• A contractor failing to install a visible, required safety railing.

In RTI, the Court held that:

• HVAC design for a BSL‑2 laboratory;
• Coordination of pressurization, filtration, and airflow; and
• Technical ceiling installation under variable pressure conditions

are not within common knowledge. Therefore, experts are needed to explain what competent professionals would have done and whether the defendants’ conduct caused RTI’s problems.

C. Summary Judgment

Summary judgment is a pretrial mechanism that ends a case (or claims) without trial when there is no genuine dispute of material fact and the moving party is entitled to judgment as a matter of law. Key points:

• The movant bears the initial burden to show the absence of disputed material facts.
• The court must view the evidence and all reasonable inferences in the light most favorable to the non-movant.
• Even if the judge believes one side is likely to win, factual disputes must be tried unless they are insubstantial or sham.

In RTI, summary judgment was proper where the lack of expert testimony meant RTI could not prove essential elements of its claims (against designArc, Pro Engineering, FM). It was improper where genuine factual disputes remained about Trane’s miswiring and Ekern’s possible vicarious liability.

D. Implied Warranties: Merchantability and Fitness for a Particular Purpose

• Implied warranty of merchantability: For goods sold by merchants, the goods are presumed fit for their ordinary, usual purpose.
• Implied warranty of fitness for a particular purpose: Arises when the seller knows the buyer’s particular purpose and that the buyer is relying on the seller’s skill or judgment to select or furnish suitable goods.

RTI alleged that Trane breached both implied warranties:

• Merchantability: The supplied HVAC equipment allegedly was not fit for its “ordinary purpose” because of how it operated with reversed wiring and erratic pressure control.
• Fitness: Trane allegedly knew RTI’s specialized needs (BSL‑2 contamination control, room-by-room pressure control) and failed to provide and/or install equipment suited to that particular purpose (¶ 22).

The Supreme Court does not definitively resolve these warranty issues but holds that factual disputes preclude summary judgment; the nature and scope of any implied warranties will be fleshed out on remand.

E. Vicarious Liability

Vicarious liability is a doctrine under which one party (often an employer or principal) is held legally responsible for the wrongful acts of another (often an employee or agent) performed within the scope of their relationship.

Here:

• Ekern contracted with Trane as its HVAC subcontractor.
• RTI claims that if Trane was negligent in miswiring the system, Ekern should be vicariously liable as Trane’s principal.

The Supreme Court does not decide whether Ekern is vicariously liable. It holds only that:

• RTI may plead and pursue that theory; and
• Summary judgment was improper because the circuit court never analyzed that separate theory (¶¶ 62–63).

F. Technical Terms: BSL‑2, HEPA, VAV, and Balancing

• BSL‑2 (Biosafety Level 2):
  A classification for labs working with agents of moderate potential hazard. Requirements include restricted access, specialized training, and use of containment equipment to manage aerosols. In facility design, BSL‑2 often entails specific airflow and filtration standards.
• HEPA (High Efficiency Particulate Air) filters:
  Filters that remove at least 99.97% of particles 0.3 microns in diameter, including many bacteria and some viruses. Critical in preventing contaminated aerosols from leaving animal rooms.
• VAV (Variable Air Volume) systems:
  HVAC systems that vary the volume of air supplied to different zones. VAV boxes in each room adjust air volume to maintain target temperatures and pressures. Erratic VAV behavior can cause sudden pressure changes, affecting ceilings and airflow patterns.
• Balancing:
  The process of adjusting airflows within an HVAC system so that each room receives the correct volume of air and maintains the desired pressure differential. In RTI’s Facility, frequent rebalancing was necessary when any room’s pressure was changed—contrary to RTI’s expectations.

VII. Conclusion

RTI, LLC v. Pro Engineering, Inc. marks a consequential development in South Dakota’s law at the convergence of construction, professional liability, and civil procedure. The Court holds that:

• Substance over form controls: Whether framed as negligence, contract, or implied warranty, claims targeting the technical sufficiency of professional or specialized construction work often require expert testimony to establish breach and causation.
• Expert qualification matters: A corporate officer’s familiarity with operations does not substitute for professional expertise in architecture, engineering, or specialized construction trades.
• Summary judgment has limits: Courts must adhere to the grounds actually raised by moving parties and respect genuine factual disputes, particularly regarding alleged miswiring and system failures.
• Pleadings should be freely amended when justice requires: Even late amendments adding negligence and vicarious liability theories should be allowed when they rest on long-known facts and cause no unfair prejudice.

On remand, RTI may pursue claims against Trane and Ekern based on both contract and tort theories, provided it marshals appropriate expert support where necessary. For future litigants and counsel, the case underscores the importance of early expert engagement, careful pleading of both contract and tort theories in complex technical disputes, and vigilant enforcement of summary judgment and amendment standards.

In sum, RTI provides a comprehensive framework for handling highly technical construction and design disputes in South Dakota, clarifying both substantive and procedural expectations and reinforcing the central role of expert testimony in such litigation.