Product Liability Explained: Design Defects, Manufacturing Defects and Failure to Warn

We rely on products every day — cars, appliances, tools, medications, medical devices, children's toys, phones and batteries. Most of the time they work as expected. But when a product is defective, it can cause serious injuries: burns from an exploding battery, amputations from a power tool without adequate guarding, brain injuries from a failed helmet, or organ damage from a dangerous drug.

Product liability law holds manufacturers, distributors and sellers responsible for injuries caused by defective products. This guide explains the legal theories behind product liability claims, the three main types of defects, common defenses, and how these cases are investigated and proven.

Who Can Be Held Responsible?

Product liability claims can potentially be brought against anyone in the chain of distribution, including:

• The manufacturer of the finished product
• Manufacturers of component parts
• Designers
• Distributors and wholesalers
• Retailers
• In some circumstances, online marketplaces, depending on their role and state law

Holding multiple parties responsible can be important when a manufacturer is foreign, insolvent or difficult to reach.

Legal Theories in Product Liability

Strict Liability

In most states, manufacturers and sellers can be held strictly liable for injuries caused by defective products. Strict liability means the injured person generally does not need to prove that the manufacturer was careless. Instead, the person must show that:

1. The product was defective
2. The defect existed when the product left the defendant's control
3. The defect caused the injury
4. The product was being used in a reasonably foreseeable way

Strict liability reflects a policy judgment that the companies that profit from products and are best positioned to make them safer should bear the cost of injuries caused by defects.

Negligence

A product liability claim may also be based on negligence — showing that the manufacturer failed to use reasonable care in designing, manufacturing, testing, inspecting or warning about the product.

Breach of Warranty

Products may come with express warranties (specific promises about the product) or implied warranties (such as the implied warranty of merchantability, that the product is fit for its ordinary purpose). Breach of warranty claims may apply when a product fails to meet these promises.

The Three Types of Product Defects

1. Design Defects

A design defect exists when the product's design itself is unreasonably dangerous — meaning every unit made according to the design shares the same flaw. Examples include:

• A vehicle prone to rolling over because of its design
• A power saw without an adequate blade guard
• A child's product with small parts that pose a choking hazard
• A battery pack without adequate protection against overheating

States use different tests to evaluate design defects:

• Consumer expectations test: whether the product failed to perform as safely as an ordinary consumer would expect when used in an intended or reasonably foreseeable manner
• Risk-utility test: whether the risks of the design outweigh its benefits, often considering whether a feasible, safer alternative design existed

Many states require proof of a reasonable alternative design — a safer design that was technologically and economically feasible and would have prevented or reduced the injury without unduly impairing the product's usefulness.

2. Manufacturing Defects

A manufacturing defect exists when a product departs from its intended design because of an error in production — a flaw that affects some units but not others. Examples include:

• A batch of tires with improperly bonded tread
• Contaminated medication
• A cracked weld in a ladder
• A battery cell with internal contamination

Manufacturing defect claims often focus on showing how the specific product differed from the manufacturer's specifications.

3. Warning Defects (Failure to Warn)

A warning defect exists when a product lacks adequate instructions or warnings about non-obvious risks that the manufacturer knew or should have known about. Examples include:

• A medication without adequate warning of a serious side effect
• A chemical product without adequate instructions for safe use
• A tool without warnings about foreseeable dangers
• Inadequate instructions for assembling or installing a product

Warnings must be reasonably clear, conspicuous and appropriate for the intended users. For prescription drugs and many medical devices, the "learned intermediary" doctrine in many states provides that warnings must be adequate for the prescribing physician.

Common Defenses in Product Liability Cases

Manufacturers and sellers raise a variety of defenses, including:

Product Misuse

The defendant may argue that the product was used in an unforeseeable way. However, manufacturers must anticipate reasonably foreseeable misuse, so this defense is not always successful.

Modification or Alteration

If the product was substantially modified after it left the manufacturer, the defendant may argue the modification caused the injury.

Comparative Fault

The injured person's own conduct may reduce recovery in many states, though states differ on how comparative fault applies in strict liability claims.

Assumption of Risk

The defendant may argue that the injured person knew of and voluntarily accepted a specific risk.

Federal Preemption

For certain products regulated by federal agencies — such as some medical devices and drugs — defendants may argue that federal law preempts state-law claims. The scope of preemption depends on the type of product and the claim.

State of the Art

Defendants may argue that the product reflected the best technology available when it was made.

Statutes of Repose

Some states bar product claims involving products older than a certain age, regardless of when the injury occurred.

Building a Product Liability Case

Preserve the Product

The product itself is usually the most important evidence. After an injury:

1. Keep the product and all its parts — do not throw anything away
2. Do not attempt to repair or alter it
3. Do not return it to the manufacturer or retailer
4. Keep packaging, manuals, receipts and labels
5. Photograph the product, the scene and your injuries
6. Note where and when you bought it

If the product is in someone else's possession — such as an insurer, employer or landlord — a preservation letter can help protect it.

Expert Analysis

Product cases typically require engineers, scientists, physicians or other qualified professionals to examine the product, identify the defect, and explain how it caused the injury. Testing may need to follow agreed protocols so that all parties can observe and evidence is not destroyed.

Discovery

Litigation may involve obtaining the manufacturer's design documents, testing records, quality control data, complaints, prior incidents, internal communications and regulatory filings. This evidence can show what the company knew and when.

Recalls and Prior Incidents

A recall, or reports of similar incidents, can be relevant evidence. However, a recall is not required to prove a defect, and a recall alone does not prove a claim.

Common Product Liability Claims

• Defective vehicles and auto parts, including airbags, seat belts, tires and brakes
• Lithium-ion battery fires in e-bikes, scooters, phones and other devices
• Defective power tools and industrial machinery
• Dangerous household appliances
• Defective children's products and toys
• Dangerous drugs and medical devices
• Contaminated food and consumer products

Frequently Asked Questions

Do I need to have purchased the product to bring a claim?

No. In most states, anyone foreseeably injured by a defective product — including bystanders — may bring a claim.

How long do I have to file a product liability claim?

Statutes of limitations and statutes of repose vary by state. Some states' repose periods bar claims based on the product's age.

What if the manufacturer is overseas?

Claims may still be possible against the manufacturer, and against domestic distributors and sellers. Jurisdictional questions can be complex.

Can I bring a claim if I was using the product incorrectly?

Possibly, if the misuse was reasonably foreseeable. The specific facts matter.

What if the product was given to me as a gift or bought secondhand?

You can generally still bring a claim. Product liability protects people foreseeably injured by a defective product, not only the original purchaser. Secondhand products may raise questions about modification or wear, but those questions are evaluated on the evidence.

Should I contact the manufacturer myself?

It is usually best to speak with an attorney first. Manufacturers may ask you to return the product for "analysis" or to sign documents that could affect your claim. You can, however, report a product safety incident to the appropriate federal agency, such as the Consumer Product Safety Commission through SaferProducts.gov, which helps regulators identify dangerous products and protect other consumers.

Crashworthiness Claims

A special type of product liability claim arises in vehicle crashes. Even when a defect did not cause the crash, a vehicle may fail to protect its occupants as well as it should have. These are called crashworthiness or "enhanced injury" claims. Examples include roofs that crush in rollovers, seat backs that collapse in rear-end collisions, fuel systems that leak and ignite, airbags that fail to deploy or deploy improperly, seat belts that unlatch, and doors that open in crashes allowing occupants to be ejected.

In crashworthiness cases, the question is typically whether a reasonable alternative design would have reduced or prevented the injuries, and how much worse the injuries were because of the defect. These claims often require extensive engineering analysis, including crash testing and computer modeling.

Medical Device and Drug Claims

Claims involving prescription drugs and medical devices present unique issues:

• Preemption: Federal law may preempt certain claims against manufacturers of high-risk medical devices that went through the FDA's premarket approval process, while devices cleared through other pathways may be treated differently. Generic drug manufacturers have also successfully argued preemption of certain failure-to-warn claims because of federal requirements that their labels match the brand-name label.
• Learned intermediary doctrine: In many states, a drug or device manufacturer's duty to warn runs to the prescribing physician.
• Causation: Proving that a drug or device caused an injury often requires scientific and medical expert testimony.
• Coordinated litigation: When many people are harmed by the same drug or device, cases may be consolidated in multidistrict litigation.

Workplace Product Injuries

Many product injuries happen at work — involving machinery, tools, scaffolding, forklifts and other equipment. Injured workers usually receive workers' compensation benefits, which generally prevent lawsuits against the employer. But workers may also have product liability claims against the manufacturers of defective equipment. These third-party claims can provide compensation not available through workers' compensation, such as pain and suffering. Common issues include missing guards, defective safety interlocks, inadequate warnings and design flaws that make injuries foreseeable.

Workplace product cases often involve questions about whether the employer modified the equipment or removed safety devices. Even then, the manufacturer may remain responsible if the modification was foreseeable or if the original design was defective.

Recalls: What Consumers Should Know

Federal agencies including the Consumer Product Safety Commission, the National Highway Traffic Safety Administration and the Food and Drug Administration oversee recalls. Consumers can search for recalls and sign up for alerts. If you own a recalled product, follow the instructions for repair, replacement or refund. Registering products when you buy them — especially car seats, cribs and other children's products — helps manufacturers contact you directly if a recall is issued, and checking recall databases before buying used products can help you avoid hazards altogether. If you were injured by a recalled product, keep the product and recall notices, and avoid sending the product back to the manufacturer before consulting an attorney.

Key Takeaways

• Manufacturers, distributors and sellers can be held responsible for injuries caused by defective products.
• Many states apply strict liability, so the injured person need not prove carelessness, only a defect that caused injury.
• The three main types of defects are design defects, manufacturing defects and warning defects.
• Preserving the product and related documents is essential.
• Defendants commonly raise misuse, modification, comparative fault and preemption defenses.

How We Can Help

At Personal Injury Lawyer Pro, our product liability attorneys work with qualified engineering and scientific professionals to identify defects and hold manufacturers accountable. If a product injured you or a loved one, contact us for a free, confidential consultation. You pay no attorney fee unless we recover compensation for you.