Manufacturing defects: The Road To a Successful Product Liability Case

When a product that works fine for everyone else fails the one time it matters, and you’re the one who gets hurt, it’s natural to wonder whether it was bad luck, your own doing or the product. If you’re not sure you even have a case, that’s normal.

Here’s the plain answer. A manufacturing defect is a flaw in how your particular unit was made: it didn’t come out of production the way the maker designed it. To recover, you generally have to show that the product was defective when it left the defendant’s control and that the defect caused your injury (in Michigan, M Civ JI 25.22, 25.32). The product itself is usually your best evidence, so keep it, unrepaired. In Michigan, you generally have three years to sue (MCL 600.5805(12)).

The obstacle is usually the claims process, not the facts: the maker’s insurer handles claims like yours every day, the key evidence is easy to lose, and the deadline runs while you recover. For product claims in general, see our complete product liability guide. Michigan’s rules are in the boxes marked “In Michigan.”

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What is a manufacturing defect?

A manufacturing defect happens in production, so only some units of a product are flawed, such as yours or one batch, while the rest are fine (Cornell Law School’s Legal Information Institute, or LII). In the Michigan Supreme Court’s words, such a product “is not in its intended condition,” and it “may be evaluated against the manufacturer’s own production standards, as manifested by that manufacturer’s other like products” (Prentis v Yale Manufacturing Co, 1984).

• A made-up example: a new electric kettle shocks its owner the first time she fills it. A wire inside her kettle was pinched against the metal body during assembly. Kettles assembled correctly don’t have that fault, and that comparison is the heart of her claim.
• Another made-up example: a machine setting drifts during one production run, so some bicycle forks are welded weaker than specified, and one snaps on an ordinary ride.

A design defect is different: it’s in the plan itself, so every unit shares it (how design defect claims work). So is a warning defect, where users weren’t given the warnings or instructions they needed (the three types of product defects). The label matters: in Michigan, a design claim against the maker is judged by a negligence, risk-utility test (Prentis). Not hurt? See your options when a defective product hasn’t injured you.

How do you prove a manufacturing defect?

Four kinds of evidence usually show what went wrong, and when.

Start with the product itself

Keep it as it was, with every piece and the packaging, and don’t repair or clean it (the checklist below lists what else to keep). If the maker, the seller or an insurer asks to take it “for inspection,” get advice first: an inspection should happen with everyone on notice and a record of what was done (how to preserve evidence).

Testing and experts

An engineer, a metallurgist or another qualified expert can examine and test the product and explain what failed. Testing that could change or destroy it should wait until everyone involved has notice and a chance to attend. Experts help, but they aren’t always required: the Michigan Supreme Court has held that “a manufacturing defect can be proved by circumstantial evidence without expert opinion testimony” (Holloway v General Motors Corp, 1978). In Michigan, a judge decides whether a scientific opinion “is reliable and will assist the trier of fact” before a jury hears it (MCL 600.2955(1)).

Comparison with units that were made right

Because a manufacturing flaw is measured against the maker’s own production standards, as shown by its other units (Prentis), comparison is central: your unit against the maker’s specifications, its inspection records and properly made units, ideally from the same batch. When a bad batch hurts many people, their claims may be brought together (how class actions and mass torts work).

Recall records and other people’s reports

Reports from other owners can show whether your failure is a one-off or part of a pattern.

• Consumer products: SaferProducts.gov, the public database of the U.S. Consumer Product Safety Commission (CPSC), holds reports of harm and recall information (15 U.S.C. § 2055a(b)(1); 84 Fed. Reg. 3134). If you file a report, the CPSC generally sends it to the maker (15 U.S.C. § 2055a(c)(1)), so stick to the facts.
• Vehicles: check your vehicle identification number (VIN) with the recall lookup of the National Highway Traffic Safety Administration (NHTSA); large automakers must send NHTSA their VIN-searchable recall data for its websites (49 C.F.R. § 573.15). NHTSA’s public complaints file contains every safety-related defect complaint it has received since January 1, 1995 (NHTSA, complaints data file).

Treat these as leads, not proof: by law, the CPSC must tell users that it doesn’t guarantee the accuracy, completeness or adequacy of its database (15 U.S.C. § 2055a(b)(5)), and a recall doesn’t prove that your unit was defective. See what a recall means for your claim.

When the product is gone, or no one can pinpoint the flaw

When the product is lost or the exact flaw can’t be found, many courts let a jury infer a defect from the circumstances. The Restatement (Third) of Torts: Products Liability, an American Law Institute treatise that courts often cite but that isn’t binding (LII), allows the inference “without proof of a specific defect” when the incident “was of a kind that ordinarily occurs as a result of a product defect” and “was not, in the particular case, solely the result of causes other than product defect existing at the time of sale or distribution” (§ 3, as quoted by New Jersey’s Supreme Court in adopting it, Myrlak v Port Authority of New York & New Jersey, 1999). Connecticut’s Supreme Court noted in 2011 that most states have adopted some form of this “malfunction theory,” but that “proof of an accident alone is insufficient” and an older product can weaken the inference (Metropolitan Property & Casualty Insurance Co v Deere & Co).

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Who can be held responsible for a manufacturing defect?

Anyone in the chain from factory to store can be: the maker of a component part, the company that assembled the product, the wholesaler and the retailer (LII). Where the flaw entered matters: if the wire in the made-up kettle example was pinched during assembly, the company that assembled the kettle is a likely target.

Is the maker strictly liable for a manufacturing defect?

In many states, yes. Product liability is generally treated as strict liability: if the product was defective and the defect caused the harm, it doesn’t matter how careful the maker was (LII). In Ohio, for example, a product that “deviated in a material way” from the maker’s specifications when it left the maker’s control can be defective “even though its manufacturer exercised all possible care” (Ohio Rev. Code § 2307.74). Michigan works differently.

What if the maker says it was your fault?

Expect to hear that you misused or changed the product, that it wore out, or that you knew the risk. You don’t have to prove you were unaware of the hazard, but depending on the state and the facts, arguments like these can reduce what you recover or, in some cases, defeat the claim.

How long do you have to file a claim?

Every state sets its own deadline; see injury deadlines in every state.

What should you keep? A checklist

• The product and every piece of it, unrepaired and uncleaned, stored out of use.
• The box, labels and manual, especially any model, serial or lot number and date code.
• Proof of purchase, such as a receipt or card statement.
• Photos and video of the product, the scene and your injuries, and witnesses’ names.
• Your medical records and bills, and proof of missed work.
• Every letter, email or recall notice from the maker, the seller or an insurer, and your written notice to the seller.

What to do next

1. Get medical care, and keep every record. Tell each provider what product was involved.
2. Secure the product as it is. Don’t repair or use it, and get advice before anyone takes it apart or takes it away.
3. Write down what happened while it’s fresh, including how long you’d had the product and how it was used and maintained.
4. Check for recalls, and notify the seller in writing if you bought the product. Don’t give a recorded statement or sign a release before you’ve had advice (what to say to an insurance adjuster).
5. Get a free case review. A lawyer can arrange testing both sides can rely on, work out who is responsible and check your deadline; get any fee agreement in writing (how injury lawyers get paid). Get a free case review, or, if you were hurt in Michigan, compare Michigan injury lawyers.

What waiting can cost

• The evidence. A product that’s repaired, used, thrown out or taken apart without notice may no longer prove anything, and in Michigan, failing to keep it can lead to sanctions against you (Brenner v Kolk).
• Your right to sue. In Michigan, generally 3 years from the injury (MCL 600.5805(12)).
• Warranty remedies. A buyer who doesn’t notify the seller within a reasonable time can be barred from any remedy (MCL 440.2607(3)(a)).

What a good outcome looks like

The product is examined in a way both sides can check, the flaw is found or fairly inferred, and the claim is filed against everyone responsible in time. Those responsible pay your medical bills and lost income and compensate you for what you went through, and you know what you’ll take home before you sign anything. From wondering whether it was bad luck or your own fault to knowing what went wrong with your unit, who answers for it and how long you have to act.

For more on defective products, drugs and toxic exposure, browse the defective product and toxic exposure guides.

Updated September 28, 2026

This guide is general information, not legal advice, and laws change. For advice about your situation, talk to a lawyer licensed in your state. Reading this page or contacting us does not create an attorney-client relationship.