How Do I Prove My Product Was Defective?

When a product causes a serious injury, one of the first questions an injured person may have is: How do I prove the product was defective? Product liability cases can arise from defective tools, machinery, household products, children’s products, medical devices, automotive components, appliances, sporting equipment, and many other consumer or commercial products. Unlike an ordinary accident case, however, proving a product liability claim often requires establishing not only that you were injured, but also that a specific defect existed and that the defect caused your injury.

The U.S. Consumer Product Safety Commission (CPSC) estimates that 38.8 million people sought medical attention in 2024 for injuries related to consumer products. That was an increase of approximately 7.6% from 2023. The CPSC cautions that these figures identify injuries associated with consumer products and do not necessarily establish that a product caused the injury.

If you believe a defective product caused your injury, preserving evidence and investigating the product promptly can be critical. An experienced Illinois product liability attorney can help determine whether the product was defective, identify potentially responsible parties, and gather the evidence necessary to establish liability.

“When a defective product causes an injury, preserving the product and the evidence surrounding the accident can be just as important as documenting the injury itself. A thorough investigation can help determine what failed, why it failed, and who may be legally responsible.” — John J. Malm, Naperville product liability lawyer

What Is a Defective Product?

A product can generally be defective because of a manufacturing defect, design defect, or inadequate warning or instructions. The precise legal requirements depend on the circumstances and the legal theory involved.

In Illinois, strict product liability law requires a plaintiff to establish that the injury resulted from a condition of the product, that the condition was unreasonably dangerous, and that the condition existed when the product left the defendant’s control. The plaintiff must also establish that the condition caused the injury. The Illinois Supreme Court has identified these as essential elements of a strict product liability claim.

A product does not necessarily have to be completely unusable to be defective. A product may function normally in many circumstances but still contain a dangerous defect that creates an unreasonable risk of injury. Common examples include:

A power tool manufactured with a defective safety mechanism.
A vehicle component that unexpectedly fails.
A ladder that collapses during ordinary use.
A children’s product containing a dangerous choking hazard.
A machine with a defective guard or safety device.
An appliance that overheats or catches fire.
A product that lacks adequate warnings about a foreseeable danger.
A medical device that fails because of a defective component.

The Three Major Types of Product Defects

Manufacturing Defects

A manufacturing defect occurs when something goes wrong during the production or assembly of an otherwise properly designed product. The particular product that injured you may differ from other products manufactured according to the intended design.

For example, suppose a manufacturer produces thousands of ladders using a particular design. If one ladder is assembled with a defective component that causes it to collapse, the problem may be a manufacturing defect.

Evidence can include the damaged product, photographs, manufacturing records, inspection records, quality-control documents, and testimony from engineers or other experts.

Design Defects

A design defect exists when the product’s design itself creates an unreasonable danger. In other words, the problem is not necessarily an isolated manufacturing mistake; the product may have been manufactured exactly according to its specifications, but those specifications may have produced an unsafe product.

Illinois courts have recognized design defects as a basis for strict product liability. Courts have considered whether a product failed to perform as safely as an ordinary consumer would expect and whether the design created an unreasonably dangerous condition.

Evidence in a design-defect case may include engineering specifications, testing results, industry standards, alternative designs, internal company documents, and expert testimony.

Failure to Warn or Instruct

Sometimes the product itself is not defective in its physical construction or design, but the manufacturer or seller may have failed to adequately warn consumers about a danger.

For example, a product might contain a chemical that can cause serious burns if used without protective equipment. If that risk is not adequately disclosed through appropriate warnings or instructions, the failure to warn may become an important part of a product liability claim.

Illinois law recognizes product liability claims involving warnings and instructions, and Illinois courts have explained that a product may be unreasonably dangerous because of a failure to warn about a danger that an average consumer would not recognize.

What Evidence Can Prove a Product Was Defective?

The evidence in a product liability case can make or break the claim. The most important piece of evidence may be the product itself.

Do not throw the product away, repair it, modify it, or discard damaged components unless your attorney advises you to do so. The physical product can potentially allow engineers and other experts to inspect exactly what happened. Important evidence may include:

The defective product and all of its components.
Photographs and videos of the product and accident scene.
Purchase receipts and invoices.
Packaging and product labels.
Owner’s manuals and instruction sheets.
Warranty information.
Serial numbers, model numbers, and manufacturing dates.
Medical records documenting the resulting injuries.
Witness statements.
Maintenance and repair records.
Product recall information.
Prior complaints involving the same product.
Manufacturer testing and inspection records.
Industry safety standards.
Expert engineering or technical analysis.

The CPSC’s National Electronic Injury Surveillance System, or NEISS, collects information concerning consumer-product-related injuries from a nationally representative sample of hospital emergency departments. This system is one of the sources used to estimate product-related injuries nationwide.

Keep the Product Exactly as It Was After the Accident

One of the biggest mistakes an injured person can make is losing or altering the evidence. Suppose a power tool breaks and causes a severe hand injury. The injured person might assume the tool should simply be repaired or discarded. But replacing the allegedly defective component could destroy evidence of the original condition.

Similarly, cleaning, modifying, repairing, or disassembling a product can potentially complicate an investigation.

If possible, preserve:

The product in its post-accident condition.
Broken or detached components.
Packaging and shipping materials.
Manuals and warnings.
Receipts and proof of purchase.
Photographs taken immediately after the incident.
Electronic records associated with the product.

An attorney may also arrange for the product to be preserved and inspected by an appropriate expert.

How Expert Witnesses Can Help Prove a Defect

Product liability cases frequently involve technical questions that cannot be answered simply by looking at the product.

An engineer, materials expert, mechanical expert, electrical engineer, human-factors specialist, or other qualified professional may be able to determine what went wrong. An expert may examine questions such as:

What was the product supposed to do?
How did the product actually perform?
What component failed?
Was the component manufactured correctly?
Was the design inherently unsafe?
Was there a safer practical alternative?
Was the danger foreseeable?
Did the product comply with applicable standards?
Did a warning adequately disclose the danger?
Did the alleged defect cause the plaintiff’s injury?

The Illinois Supreme Court has emphasized that a plaintiff bears the burden of proving the required elements of a strict product liability claim, including the defective condition, unreasonable danger, existence of the condition when the product left the defendant’s control, injury, and proximate causation.

Recalls Can Provide Important Evidence

A product recall does not automatically prove that a particular injured person’s product was defective or that a manufacturer is legally liable. However, recall information can be an important investigative lead.

For example, NHTSA reported 891 vehicle recalls affecting approximately 29.3 million vehicles in 2025, including 649 defect recalls affecting approximately 21.8 million vehicles.

If your product has been recalled, an attorney may investigate:

The reason for the recall.
Whether your particular model or serial number was included.
When the manufacturer learned about the problem.
Whether similar incidents had previously been reported.
What corrective action was recommended.
Whether you received a recall notice.
Whether the recalled defect resembles the condition that caused your injury.

Even when no recall exists, however, a product may potentially be defective. A recall is not necessarily required to establish a product liability claim.

Proving That the Defect Caused Your Injury

Showing that a product was defective is only part of the case. You generally must also connect the defect to your injury. Consider a defective ladder. If an investigation establishes that the ladder contained a manufacturing defect, the next question is whether that defect actually caused the ladder to collapse and caused the plaintiff’s injuries.

Medical evidence is therefore important. Medical records can document the nature and severity of the injury and help establish when and how it occurred. Other evidence may include accident reconstruction, biomechanical analysis, photographs, eyewitness testimony, surveillance video, and expert testimony.

What If the Product Was Used for Something Other Than Its Intended Purpose?

This can become a significant issue in product liability litigation. Manufacturers may argue that an injured person was using a product improperly or in a way that was not reasonably foreseeable. Whether that argument defeats a claim depends heavily on the circumstances.

Illinois courts have recognized that strict liability concerns products that are unreasonably dangerous in light of their nature and intended or reasonably expected use. That means an investigation should examine exactly how the product was being used, whether that use was foreseeable, what instructions accompanied the product, and whether the manufacturer anticipated similar uses.

What If the Manufacturer Says You Caused the Accident?

Manufacturers and insurers may challenge a product liability claim by arguing that the product was not defective or that the plaintiff’s own conduct caused the accident. That is another reason evidence matters.

An injured person’s attorney may need to reconstruct the accident and determine whether the alleged misuse actually caused the injury or whether the product itself created the dangerous condition.

The fact that an injured person made a mistake does not necessarily mean there was no product defect. The legal analysis depends on the facts, the product, the applicable law, and the evidence.

What Should I Do After a Defective Product Injury?

If you believe a defective product injured you, take steps to protect the evidence as soon as possible.

Seek appropriate medical attention.
Keep the product and its components.
Photograph the product and accident scene.
Save receipts, packaging, manuals, and warnings.
Write down what happened while your memory is fresh.
Identify witnesses.
Avoid making repairs or modifications to the product.
Report the incident to the appropriate authorities when appropriate.
Do not give a recorded statement to an insurer before understanding your legal rights.
Contact a product liability attorney promptly.

Timing can also matter. Illinois has specific rules governing product liability claims, including a statute of repose that can limit when certain product liability actions may be filed. The Illinois statute generally contains 10- and 12-year periods tied to the product’s first sale or delivery, subject to statutory exceptions. Because the deadlines can depend on the facts, an injured person should not assume that simply because an accident occurred recently, there is unlimited time to investigate or file a claim.

Frequently Asked Questions About Proving a Defective Product

Do I need to have the product to bring a product liability case?

Not necessarily, but preserving the product can be extremely valuable. Other evidence may include photographs, videos, receipts, witness testimony, medical records, recall information, and expert analysis. Losing the product can make proving the defect more difficult.

Does a product have to be recalled for me to have a claim?

No. A recall can provide useful information, but the absence of a recall does not necessarily mean a product was safe or free from defects.

Who can be responsible for a defective product?

Potentially responsible parties can include manufacturers, distributors, sellers, and other entities involved in placing the product into the stream of commerce. The appropriate defendants depend on the facts and applicable law.

What if I bought the product online?

Buying a product online does not automatically prevent a product liability claim. The identity and role of the manufacturer, seller, distributor, marketplace, and other entities may need to be investigated.

Contact the Experienced Illinois Product Liability Lawyers at John J. Malm & Associates If You Have Been Injured

Proving that a product was defective is often much more complicated than simply showing that something broke. A successful product liability investigation may require preserving the product, determining the type of defect, reviewing warnings and instructions, researching recalls and prior incidents, analyzing manufacturing and design evidence, consulting qualified experts, and establishing that the defect caused your injuries. With millions of people receiving medical treatment each year for injuries associated with consumer products, defective-product cases can involve significant physical, financial, and emotional consequences.

If you’ve been injured because a product malfunctioned, broke, lacked adequate warnings, or otherwise exposed you to an unreasonable risk of harm, do not discard the product or important evidence before speaking with an attorney. Contact John J. Malm & Associates for a free case evaluation. Our Illinois personal injury attorneys can investigate what happened, identify potentially responsible parties, preserve critical evidence, and pursue the compensation you may be entitled to under Illinois law.