Torts: Products Liability

Products liability is the area of tort law that assigns responsibility when a product injures someone because it is defective. The central idea is straightforward: products placed into the stream of commerce should be reasonably safe when used as intended or in a reasonably foreseeable way. When they are not, injured consumers may seek compensation from those responsible for making, designing, marketing, or distributing the product.

Modern products liability claims generally arise under two main theories of recovery: negligence and strict liability. Although both can lead to similar damages, they differ in what the plaintiff must prove and how courts evaluate fault. Within those theories, defects typically fall into three categories: manufacturing defects, design defects, and failure to warn.

Theories of Recovery: Negligence and Strict Liability

Negligence: Focusing on Unreasonable Conduct

Negligence asks whether the defendant acted unreasonably under the circumstances. In a products case, that typically means the plaintiff must prove:

• The defendant owed a duty of reasonable care (for example, to design, manufacture, inspect, or warn)
• The defendant breached that duty
• The breach caused the injury (actual and proximate cause)
• The plaintiff suffered damages

Negligence fits naturally with conduct-based questions: Was quality control careless? Were safety tests skipped? Did the company ignore known hazards? The plaintiff often relies on evidence about internal practices, industry standards, regulatory compliance, testing protocols, and what the defendant knew or should have known at the time.

Negligence can be powerful, but it can also be demanding. Proving unreasonable conduct may require substantial discovery and expert testimony, especially when the product is complex.

Strict Liability: Focusing on the Product’s Condition

Strict products liability shifts the emphasis from the defendant’s conduct to the product’s defectiveness. Under strict liability, the plaintiff generally must show:

• The product was defective
• The defect existed when it left the defendant’s control
• The defect was a factual and legal cause of the injury
• The plaintiff suffered damages

Strict liability does not mean “automatic liability.” Plaintiffs still must prove a defect and causation. The key difference is that the plaintiff does not need to show the defendant acted negligently. The law imposes responsibility because those who profit from selling products are often in the best position to prevent harm, spread losses through pricing or insurance, and improve safety.

Strict liability most commonly targets manufacturers, but it can also extend to others in the distribution chain, depending on jurisdiction and the role each party played.

Types of Product Defects

Manufacturing Defects: A Product That Deviates from Its Intended Design

A manufacturing defect occurs when a specific unit differs from the manufacturer’s own design or specifications, making it more dangerous than consumers expect. The design might be safe on paper, but something went wrong during production, assembly, or quality control.

Common examples include:

• Contamination in food or pharmaceuticals
• A cracked component due to improper heat treatment
• Missing safety features that should have been installed
• A mislabeled concentration or dosage

Manufacturing defect claims often focus on the particular item that caused the injury rather than the entire product line. Because the deviation can be easier to conceptualize, these claims can be more straightforward than design defect cases, though plaintiffs still must connect the defect to the harm and show it existed when the product left the defendant’s control.

Design Defects: The Product Is Unreasonably Dangerous as Designed

Design defects involve the blueprint itself. The product line is manufactured as intended, but the intended design creates unreasonable risks. These cases tend to be heavily expert-driven because courts must evaluate safety tradeoffs, engineering feasibility, and whether safer alternatives were available.

Courts often analyze design defect claims using tests that examine consumer expectations, risk-utility balancing, or the availability of a reasonable alternative design. However framed, the core question is whether the design’s risks outweigh its benefits in a way that tort law should treat as defective.

Practical factors that often matter include:

• The severity and likelihood of foreseeable harm
• The product’s utility and purpose
• The feasibility of a safer design
• The cost of an alternative design relative to the safety gain
• Whether the alternative would impair the product’s usefulness

Design cases frequently arise in vehicles, industrial machinery, consumer electronics, and medical devices, where even small design choices can affect safety outcomes. A plaintiff’s argument typically centers on preventability: a safer design was realistically achievable without destroying the product’s function or pricing it out of the market.

Failure to Warn: Inadequate Instructions or Safety Warnings

Even a well-designed, well-manufactured product can be dangerous if users are not properly warned about non-obvious risks. Failure to warn claims focus on the product’s labeling, instructions, and safety communications. A warning is not just a sticker. It is part of the product because it shapes how the product is used.

A plaintiff generally must show:

• The product posed risks that required a warning
• The warnings or instructions were inadequate (missing, unclear, buried, or misleading)
• The inadequate warning caused the injury, often by affecting how the plaintiff used the product

Warnings are especially important for products with inherent risks, such as chemicals, power tools, prescription drugs, and medical devices. The adequacy of a warning can turn on content, clarity, prominence, and whether it reasonably reaches the expected user.

Failure to warn also includes failure to provide proper instructions for safe use. If a product requires a specific setup, maintenance procedure, or protective equipment, the absence of those instructions can be a defect in itself.

Causation and Proof: Connecting the Defect to the Injury

Across all product liability theories, causation is pivotal. Plaintiffs must prove that the defect was a factual cause of their injury and that the injury was a foreseeable result of the defect. In practice, this often involves:

• Preserving the product and documenting its condition
• Engineering, medical, or human-factors experts
• Evidence of similar incidents, recalls, or internal reports, when available
• Differentiating product-caused harm from misuse, wear and tear, or unrelated medical conditions

Because products cases can involve technical systems and multiple actors, parties often dispute whether the product was defective, whether it was altered after sale, and whether the user’s conduct broke the causal chain.

Defenses in Products Liability Cases

Defenses vary by jurisdiction and theory, but several appear repeatedly in litigation. They often focus on responsibility allocation, causation, and whether the plaintiff’s conduct or other events account for the injury.

Misuse and Unforeseeable Use

If the product was used in a way the manufacturer could not reasonably anticipate, the defendant may argue that the misuse defeats liability. Foreseeability matters. Many products are routinely used in imperfect ways, and manufacturers may be expected to anticipate common deviations from ideal use.

Assumption of Risk

If the plaintiff knew of the specific danger and voluntarily proceeded, the defendant may raise assumption of risk. This defense often arises where warnings were given but allegedly ignored, or where the user had specialized knowledge about the hazard.

Comparative or Contributory Fault

Some jurisdictions reduce recovery if the plaintiff’s own negligence contributed to the injury. For example, failing to follow instructions, disabling safety guards, or using incompatible replacement parts can become fault issues even in a strict liability framework, depending on the jurisdiction’s approach.

Product Alteration or Substantial Modification

If the product was materially altered after it left the defendant’s control, and that change caused the injury, the defendant may avoid liability. This defense is common with machinery where guards are removed, or with consumer products that are repaired using nonconforming parts.

State of the Art and Knowledge at the Time

Especially in design and warning cases, defendants may argue that the risk was not knowable given the scientific and technical knowledge available at the time of sale. This defense intersects with what testing was feasible and what hazards were reasonably discoverable.

Practical Takeaways: How Products Liability Works in Real Disputes

Products liability claims tend to turn on a small set of practical questions:

• What exactly was defective: the specific unit, the design, or the warning?
• When did the defect arise: before or after the product left the defendant’s control?
• Could the harm have been prevented through reasonable design changes, manufacturing controls, or warnings?
• Did the user’s conduct, maintenance, or modification contribute to the outcome?

Understanding the structure of products liability helps separate a truly defective product from an unfortunate accident that the law does not treat as actionable. Negligence focuses on the reasonableness of conduct. Strict liability focuses on whether the product was defective when sold. Manufacturing defects, design defects, and failure to warn provide the core framework for analyzing what went wrong and who should bear the cost when a product causes injury.