The framework, the doctrines, the principles of safe design and safe warnings, and the practical realities of investigating and litigating a products case

Product liability in Missouri is a hybrid creature, and the practitioner who forgets it will misstate the law. It began as judge-made doctrine—the Supreme Court adopted strict liability in tort in 1969—and was later overlaid, but never displaced, by the 1987 tort-reform statutes now codified at sections 537.760 to 537.765 RSMo. The cause of action lives in the common law; the elements are framed by statute; and the phrase that decides most cases, “unreasonably dangerous,” is left deliberately undefined for the jury. Layered on top are doctrines that do not appear in the statute at all—crashworthiness, the learned intermediary rule, the evidentiary treatment of recalls—and a set of practical realities, from evidence preservation to the economics of expert proof, that determine whether a meritorious claim can actually be tried.

I. The Two Sources: Common Law and Chapter 537

Missouri joined the strict-liability movement in Keener v. Dayton Electric Manufacturing Co., 445 S.W.2d 362 (Mo. 1969), adopting Restatement (Second) of Torts § 402A after a man was electrocuted lifting an ungrounded sump pump. Under Keener, one who sells a product in a defective condition unreasonably dangerous is liable for resulting harm if it is in the business of selling the product and the product reaches the user “without substantial change in the condition in which it is sold,” 445 S.W.2d at 364—and liability attaches “even though the seller has exercised all possible care,” and regardless of privity. Strict liability asks about the condition of the product, not the conduct of the manufacturer. The design branch was added in Blevins v. Cushman Motors, 551 S.W.2d 602 (Mo. banc 1977).

The 1987 tort-reform package added sections 537.760 through 537.765, which define the claim, protect innocent sellers, install pure comparative fault, and create a narrow state-of-the-art defense. The Supreme Court has read these statutes as a codification of the § 402A standard rather than a replacement of the common law—indeed, as a tacit legislative adoption of the approach of leaving “unreasonably dangerous” undefined. Rodriguez v. Suzuki Motor Corp., 996 S.W.2d 47, 65 (Mo. banc 1999). The working lawyer therefore reads § 402A, the Keener–Blevins–Nesselrode line, and Chapter 537 together, and resists importing the risk-utility and reasonable-alternative-design regime of the Restatement (Third), which Missouri has repeatedly declined to adopt.

II. The Statutory Definition of a “Products Liability Claim”

Section 537.760 defines a “products liability claim” as one seeking damages on a strict-liability theory because (1) the defendant, “wherever situated in the chain of commerce,” transferred a product in the course of its business; (2) the product was used in a manner reasonably anticipated; and (3) either or both of the following: (a) the product was then in a defective condition unreasonably dangerous when put to a reasonably anticipated use, and the plaintiff was damaged as a direct result of that condition as it existed when sold; or (b) the product was then unreasonably dangerous when put to a reasonably anticipated use without knowledge of its characteristics, and the plaintiff was damaged as a direct result of the product being sold without an adequate warning.

Two structural points are frequently miscited. Subsection (3) splits the tort into two branches—the defect branch of (3)(a), housing both design and manufacturing defects, and the failure-to-warn branch of (3)(b); the warning theory should be cited to (3)(b), not (2)(b). And “reasonably anticipated use” is an affirmative element the plaintiff must prove, appearing in both subsection (2) and (3)(a); it “includes misuse and abnormal use which is objectively foreseeable,” Nesselrode v. Executive Beechcraft, Inc., 707 S.W.2d 371, 380–81 (Mo. banc 1986).

III. The Three Theories of Defect, With Illustrations

Missouri recognizes three theories under the single statutory standard. Each is treated in depth in a companion article; a single illustrative case conveys the flavor of each.

Design defect indicts the blueprint: the product was built as intended, but the design makes the whole line unreasonably dangerous. Blevins v. Cushman Motors is the archetype—a three-wheeled golf cart that skidded and rolled on a shaded slope, where evidence that a wider wheelbase, a fourth wheel, and a lower center of gravity would have made the cart stable was enough to submit the case, 551 S.W.2d at 608. (See Design Defect Claims Under Missouri Law and Safer Alternative Design Requirements.)

Manufacturing defect indicts the individual unit: it departed from its own specification and is more dangerous than its siblings. Because that unit is often destroyed in the injuring event, Missouri permits proof by circumstantial inference, as in Klein v. General Electric Co., 714 S.W.2d 896, 900 (Mo. App. 1986), where a coffeemaker consumed in the house fire it started could still be found defective because the plaintiffs’ experts eliminated other ignition sources. (See Manufacturing Defect Claims Under Missouri Law.)

Failure to warn contends that a product sound in design and manufacture is unreasonably dangerous because it was sold without an adequate warning of a hazard the user did not know—as in Grady v. American Optical Corp., 702 S.W.2d 911 (Mo. App. 1985), where “safety glasses” warned only that the lenses were “not unbreakable,” without warning that they could shatter into the wearer’s eye. (See Failure-to-Warn Claims Under Missouri Law.)

IV. “Unreasonably Dangerous”: The Undefined Standard

The most distinctive feature of Missouri products law is that its courts have refused to define the phrase that decides the case. Nesselrode held that “the concept of unreasonable danger . . . is presented to the jury as an ultimate issue without further definition,” 707 S.W.2d at 377, and declined to adopt either the consumer-expectation or the risk-utility test. Rodriguez reaffirmed the refusal and rejected the Restatement (Third)’s reasonable-alternative-design theory; and Moore v. Ford Motor Co., 332 S.W.3d 749, 760 (Mo. banc 2011), stated the consequence flatly: “Missouri does not require a plaintiff to create an alternative design to prove a design defect claim.” There is thus no test the plaintiff must satisfy and none the defendant may demand by instruction. Yet the federal courts applying Missouri law import a functional consumer-expectations and open-and-obvious gloss to resolve cases as a matter of law—Linegar v. Armour of America, Inc., 909 F.2d 1150, 1154 (8th Cir. 1990) (“[a] manufacturer is not obliged to market only one version of a product, that being the very safest design possible”)—so the formal doctrine and the functional doctrine diverge, and the practitioner must command both.

V. The Principles of Safe Design

Beneath the doctrine lie engineering principles that Missouri juries, lawyers, and experts return to again and again. The first is the safety hierarchy: a reasonably safe product design eliminates a hazard where feasible, guards against it where it cannot be eliminated, and warns of the residual risk that remains—in that order. A warning is the last line of defense, not a substitute for a safer design, which is why Moore holds that an adequate warning does not cure a defective design and a sound design does not excuse an inadequate warning; the two are independent. The second principle is foreseeable use and misuse: the design must account not only for intended use but for uses the manufacturer should reasonably anticipate, including foreseeable misuse and the conditions of maintenance and repair, Nesselrode, 707 S.W.2d at 380–81; Jarrell v. Fort Worth Steel & Manufacturing Co., 666 S.W.2d 828, 835–36 (Mo. App. 1984) (manufacturer should have anticipated that maintenance workers would reach into the auger housing).

The third principle is the reasonable-manufacturer frame drawn from Blevins and the Oregon Phillips v. Kimwood decision it adopted: strict liability asks about the dangerousness of the product as designed, but the jury may think about what a reasonable manufacturer, knowing the risk, would have done—so risk-utility reasoning and feasible-alternative evidence inform the analysis without becoming a required test. A demonstrated safer alternative is, in practice, the single most persuasive proof a design plaintiff can offer, even though Missouri does not make it an element; the companion article, Safer Alternative Design Requirements, explains why plaintiffs prove it anyway. The fourth principle is the limit: the existence of a safer possible design does not by itself establish liability, because a manufacturer may offer more than one version of a product and consumers may reasonably choose utility, cost, or comfort over maximum safety (Linegar). Safe design in Missouri is thus a question of reasonable engineering judgment presented to a jury, not a search for the theoretically safest artifact.

VI. The Principles of Safe Warnings

The warning cases yield their own set of principles. A warning must signal the specific danger—not merely identify the product or instruct on its use. A caution that lenses are “not unbreakable” was inadequate because it did not warn that they could shatter toward the eye (Grady, 702 S.W.2d at 917), and installation instructions and part numbers are not warnings at all (Nesselrode, 707 S.W.2d at 387). A warning must be adequate in content, prominence, and timing, judged by “placement or location, the language used and how it may or may not impress the average user” (Grady, 702 S.W.2d at 917); a warning positioned where the user will not see it, or delivered too late to matter, can be found inadequate as a matter of fact. And the warning must reach the user—the manufacturer generally cannot delegate the duty to an employer or intermediary.

Two limits cabin the duty. There is no duty to warn of open, obvious, or commonly known dangers, though obviousness is usually itself a jury question. And in prescription-drug and medical-device cases the duty is redirected by the learned intermediary doctrine to the prescribing physician (Part IX). Missouri aids warning plaintiffs with a rebuttable presumption that an adequate warning would have been read and heeded—but the presumption is a submissibility device, not a jury instruction, and it never arises where the plaintiff already knew the danger. Arnold v. Ingersoll-Rand Co., 834 S.W.2d 192, 194 (Mo. banc 1992); Tune v. Synergy Gas Corp., 883 S.W.2d 10, 14 (Mo. banc 1994). The warning claim, in short, is a causation claim, and the plaintiff’s knowledge is the hinge on which duty, causation, and the presumption all turn. (See Failure-to-Warn Claims Under Missouri Law.)

VII. Crashworthiness and the Second Collision

Some of the most consequential Missouri products cases are not about whether a product caused an accident, but about whether it made the resulting injuries worse. The crashworthiness or “second collision” doctrine holds that a vehicle manufacturer must design a product reasonably safe not only for its ordinary function but for the foreseeable impact of the occupant against the vehicle in a crash, and that it may be liable for injuries it did not cause but enhanced because the product was not reasonably crashworthy. The doctrine originates in Larsen v. General Motors Corp., 391 F.2d 495 (8th Cir. 1968), and Missouri adopted it in Cryts v. Ford Motor Co., 571 S.W.2d 683 (Mo. App. E.D. 1978). A collision, in other words, is a reasonably anticipated use of an automobile—the manufacturer cannot argue that no one is supposed to crash.

The doctrinally critical point is the apportionment of the enhanced injury, and here Missouri’s rule favors the plaintiff. A crashworthiness plaintiff need not prove with precision which injuries flowed from the defect as opposed to the collision; it is enough to prove that the defect “was a substantial factor in producing damages over and above those which were probably caused . . . by the original impact,” and where the enhanced injury is indivisible, the manufacturer is a concurrent tortfeasor jointly and severally liable for the whole. Bass v. General Motors Corp., 150 F.3d 842, 842–43 (8th Cir. 1998) (applying Missouri law); Richardson v. Volkswagenwerk, A.G., 552 F. Supp. 73, 80, 83 (W.D. Mo. 1982). The modern anchors are Moore (a seatback that collapsed rearward in a rear-end collision; foreseeable that seats yield and that heavier occupants use the vehicle) and Bavlsik v. General Motors, LLC, 870 F.3d 800 (8th Cir. 2017), which recognized that a manufacturer’s failure to test a restraint system for a foreseeable rollover is an independent negligent-design theory, distinct from proving a specific alternative design.

Two interactions deserve flagging. Seat-belt non-use, which is barred as comparative-negligence evidence in ordinary auto cases and capped at a one-percent reduction under section 307.178.4 RSMo, is fully admissible in a products or crashworthiness case: section 307.178.5 exempts actions “arising out of the design, construction, manufacture, distribution, or sale of a motor vehicle,” in which non-use “shall be admissible as evidence of comparative negligence or fault, causation, absence of a defect or hazard, and failure to mitigate damages.” This is a major, products-specific defense tool. Second, ordinary negligence in causing the underlying collision—speeding, inattention—is not among the enumerated fault categories of section 537.765, so there is a strong argument that a plaintiff’s accident-causing fault does not reduce a strict-liability enhanced-injury recovery; the point is not squarely settled in Missouri and should be briefed as such. Crashworthiness cases are expert-intensive, turning on accident reconstruction, occupant kinematics, and injury-causation opinions that must clear the post-2017 Daubert standard of section 490.065.2 RSMo.

VIII. Investigation and the Preservation of Evidence

More products cases are lost in the first weeks than in the courtroom, because the evidence that proves or disproves a defect is physical, perishable, and often in someone else’s hands. The threshold task is to preserve the product. The unit that failed—and, where possible, exemplar units—should be located, photographed and videotaped in place before anyone handles it, secured under a documented chain of custody, and protected from alteration, repair, or disposal. Preservation and litigation-hold letters should go promptly to every party and custodian who may control the product, component parts, maintenance records, and electronic data. Where more than one party will examine the item, a written joint inspection protocol—and, before any teardown, a destructive-testing stipulation specifying notice, the sequence of non-destructive imaging before cutting, the preservation of removed components, and court approval where the unit is irreplaceable—prevents the examination itself from becoming a source of liability.

The reason for this discipline is spoliation. Missouri’s spoliation doctrine permits an adverse inference—holding the spoliator “to admit that the missing evidence would have been unfavorable to its position,” Marmaduke v. CBL & Associates Management, Inc., 521 S.W.3d 257, 269 (Mo. App. E.D. 2017)—but only on a showing of intentional destruction under circumstances manifesting fraud, deceit, or bad faith; negligent loss does not suffice, and the timing of destruction alone is not enough. Schneider v. G. Guilliams, Inc., 976 S.W.2d 522, 527 (Mo. App. E.D. 1998); Brown v. Hamid, 856 S.W.2d 51, 56–57 (Mo. banc 1993); DeGraffenreid v. R.L. Hannah Trucking Co., 80 S.W.3d 866, 873 (Mo. App. W.D. 2002)(overruled on other grounds). The doctrine is a two-edged sword: a defendant that scraps the accident unit risks the inference, and a plaintiff who discards it before the defense can inspect risks it too. The mere unavailability of a product that was lost without bad faith goes to the weight of the evidence, not to a complete failure of proof, so a diligent plaintiff can still reach the jury circumstantially—but no one should rely on that grace when preservation is within reach.

Finally, the cost of doing this well is a strategic reality, not an afterthought. A contested products case routinely requires several experts—an engineer or metallurgist on the defect, an accident reconstructionist, a biomechanist or medical expert on causation, sometimes a human-factors or warnings specialist—whose investigation, testing, and testimony commonly run into the tens and often hundreds of thousands of dollars, before accounting for product acquisition and storage, destructive testing, and the travel and inspection those experts require. Because the plaintiff ordinarily bears these costs, and because the post-2017 Daubert standard rewards early, well-funded expert work, counsel must make a candid economic assessment at intake: whether the projected damages justify the investment the defect proof will demand. That calculus, and the mechanics of preservation, inspection, and spoliation, will be developed in a forthcoming article in this series devoted to investigating the products case.

IX. Specialty Areas: Prescription Drugs and Medical Devices

Drug and device cases follow the general framework but are governed by two overlays that can be dispositive. The first is the learned intermediary doctrine: because prescription products reach the patient only through a physician’s individualized judgment, the manufacturer’s duty to warn runs to the prescriber, and an adequate warning to the physician discharges it. Missouri adopted the rule in Krug v. Sterling Drug, Inc., 416 S.W.2d 143 (Mo. 1967), and extended it to devices in Kirsch v. Picker International, Inc., 753 F.2d 670 (8th Cir. 1985); its practical teeth are on causation, because a prescriber’s independent knowledge of the risk, or testimony that she would have prescribed regardless, defeats the claim as a matter of law. The second overlay is federal preemption, which must be analyzed first, before the doctrine. Brand-name drug warning claims generally survive (Wyeth v. Levine, 555 U.S. 555 (2009)); generic-drug warning and design claims are generally preempted (PLIVA, Inc. v. Mensing, 564 U.S. 604 (2011); Mutual Pharmaceutical Co. v. Bartlett, 570 U.S. 472 (2013)); and device claims turn on the FDA pathway—premarket-approved Class III devices are largely barred except for parallel claims (Riegel v. Medtronic, Inc., 552 U.S. 312 (2008)), while section 510(k)-cleared devices generally are not (Medtronic, Inc. v. Lohr, 518 U.S. 470 (1996)). These cases are, for that reason, as much about FDA regulatory law as about state tort law. (See The Learned Intermediary Doctrine in Missouri Products Cases.)

X. Mass Torts, Multidistrict Litigation, and Class Actions

Many modern products claims—talc, glyphosate, pelvic mesh, metal-on-metal hips, and pharmaceuticals—arise not as isolated suits but as components of a mass tort, and the Missouri practitioner must understand how these aggregate. It is essential to distinguish mass torts from class actions. Personal-injury products claims are generally not certifiable as class actions, because individualized questions of exposure, medical causation, comparative fault, and damages overwhelm any common issues; the federal foundations are Amchem Products, Inc. v. Windsor, 521 U.S. 591 (1997), and Ortiz v. Fibreboard Corp., 527 U.S. 815 (1999), and Missouri’s Rule 52.08 imposes the same predominance requirement. Such claims therefore proceed as individually filed but coordinated cases. Economic-loss products claims—mislabeling, deceptive marketing, paying a premium for a product that did not perform—are a different matter, and are often brought as class actions under the Missouri Merchandising Practices Act, sections 407.020 and 407.025 RSMo, though the 2020 reforms of Senate Bill 591 tightened certification by requiring a reasonable-consumer standard and individualized, objective proof of ascertainable loss.

Missouri, and the City of St. Louis in particular, was for a time a prominent mass-tort forum, a reputation crystallized by the talc litigation and the Ingham v. Johnson & Johnson verdict—$4.69 billion, reduced on appeal to roughly $2.1 billion, 608 S.W.3d 663 (Mo. App. E.D. 2020), cert. denied (2021). Two developments reshaped that landscape. The first is constitutional: Bristol-Myers Squibb Co. v. Superior Court, 582 U.S. 255 (2017), held that a state court lacks specific jurisdiction over the claims of non-resident plaintiffs against a non-resident manufacturer absent an affiliation between the forum and their claims, dismantling the practice of bundling out-of-state plaintiffs into a single St. Louis petition; Ford Motor Co. v. Montana Eighth Judicial District Court, 592 U.S. 351 (2021), later confirmed that jurisdiction over a resident’s in-state injury does not require the product to have been designed or built in the forum. The second is statutory: Missouri’s 2019 venue-and-joinder reform (Senate Bill 7) fixed tort venue in the county where the plaintiff was first injured, provided that separate purchases of the same product do not satisfy the joinder standard, and directed severance and transfer of misjoined plaintiffs—codifying the Bristol-Myers Squibb logic as a matter of state procedure.

The federal counterpart is multidistrict litigation: under 28 U.S.C. § 1407, the Judicial Panel on Multidistrict Litigation consolidates federal cases sharing common questions for coordinated pretrial proceedings, though the transferee court cannot try them and must remand for trial (Lexecon Inc. v. Milberg Weiss, 523 U.S. 26 (1998)). For the Missouri practitioner the strategic questions follow directly: whether a Missouri-connected plaintiff can and should remain in state court, where the forum is often more favorable; how to coordinate common discovery and experts with MDL leadership; and how to navigate the defense counter-moves of removal on diversity grounds and, for MMPA class actions, removal under the Class Action Fairness Act, 28 U.S.C. § 1332(d). After Bristol-Myers Squibb and Senate Bill 7, the center of gravity for out-of-state claimants has shifted to the federal MDL, with Missouri state court reserved, in the main, for Missouri-connected plaintiffs.

XI. The Principal Defenses

The defenses recur across every theory. Section 537.765 applies pure comparative fault, reducing damages by the plaintiff’s share of enumerated fault—misuse, knowing and unreasonable exposure to a danger, failure to mitigate—without barring recovery. Section 537.764 makes state of the art a complete affirmative defense, but only in strict-liability failure-to-warn cases and only on the defendant’s proof that the danger was neither known nor reasonably discoverable at sale. Misuse outside reasonable anticipation defeats the prima facie case, while a substantial post-sale alteration breaks the causal chain. The innocent-seller statute, section 537.762, lets a non-manufacturing seller obtain dismissal where the manufacturer or another fully recoverable defendant is before the court; the 2019 amendment repealed the clause that had preserved venue notwithstanding the seller’s dismissal, so dismissing a resident retailer can now open the door to removal. And in drug and device cases, federal preemption can extinguish a claim before the merits (Part IX).

XII. Timing: Limitations and Accrual

Personal-injury and property-damage products claims are governed by the five-year limitation of section 516.120(4) RSMo, with accrual measured under section 516.100 from the point the damage is “sustained and capable of ascertainment”—an objective inquiry that begins when a reasonably prudent person would be on notice of a potentially actionable injury, Powel v. Chaminade College Preparatory, Inc., 197 S.W.3d 576 (Mo. banc 2006). A products claim brought as a wrongful-death action instead runs on the three-year period of section 537.100, generally from the death. Because the choice of theory can move the clock—and because, in mass-tort and latent-injury contexts, accrual can be sharply contested—limitations analysis should precede, not follow, the framing of the complaint.

XIII. How This Series Fits Together

The doctrines surveyed here are examined in depth across the companion articles. Read in sequence, they move from the general framework to the specific proof problems and evidentiary fights that decide Missouri products cases—the undefined standard and the design claim it governs; the circumstantial proof of a manufacturing defect and its collision with Daubert; the two causation prongs and the read-and-heed presumption of the warning claim; the reasonable-alternative-design inquiry Missouri treats as evidence rather than an element; the Pollard framework for recalls and remedial measures; and the learned intermediary doctrine and its preemption overlay. A forthcoming article will address the investigation and preservation of evidence in detail. Together they describe a body of law both stable and distinctive: the jury decides what “unreasonably dangerous” means, and the lawyer who best fills that vacuum—with evidence, with a preserved product, and with argument—is the one who prevails.

Related in the Products Liability Series

• Design Defect Claims Under Missouri Law — the undefined “unreasonably dangerous” standard and how design cases are submitted.
• Manufacturing Defect Claims Under Missouri Law — proving departure from design by circumstantial inference and expert proof.
• Failure-to-Warn Claims Under Missouri Law — the two causation prongs and the read-and-heed presumption.
• Safer Alternative Design Requirements — why Missouri treats alternative design as evidence, not an element.
• Product Recall Evidence in Civil Litigation — the Pollard framework and the limits on recall admissibility.
• The Learned Intermediary Doctrine in Missouri Products Cases — the physician as the object of the duty to warn, and the preemption overlay.
• Investigating the Products Case: Preservation, Spoliation, and Cost.