New Hampshire Product Liability Law: Design Defects, Warnings & Legal Time Limits~5 min read

Product liability refers to the legal responsibility of manufacturers, distributors, retailers, and others in the supply chain for injuries or damages caused by a product. In New Hampshire, as in many states, there are statutes and case law that shape how product liability claims work. This blog explains the framework, important concepts, time limits, defenses, and recent developments in NH product liability law.

What Is a Product Liability Action?

Under New Hampshire law (RSA Chapter 507‑D, “Product Liability Actions”), a product liability action is broadly defined. It includes any lawsuit for injury, death, property damage, or other harm that arises from:

• The design, manufacture, assembly, or construction of a product
• Warnings, instructions, labeling, or packaging
• Marketing, advertising, or certifying of a product
• Other related steps such as testing, instruction, or product modification
• This definition covers all legal theories: strict liability, negligence, breach of warranty, failure to warn or instruct, misrepresentation, and more.

Types of Defects

Claims generally fall into a few categories of defect:

1. Manufacturing defect – where something went wrong when the product was being made, such that it does not conform to the intended design.
2. Design defect – where the design itself is unreasonably dangerous for its intended or reasonably foreseeable use. New Hampshire courts use a risk‑benefit balancing test to assess whether a design is unreasonably dangerous.
3. Failure to warn (or inadequate warnings/instructions) – even a well‑made and well‑designed product may be dangerous in foreseeable ways; the manufacturer or seller may have a duty to warn of those dangers or to provide safe instructions for its use.

Time Limits (Statute of Limitations)

One of the critical issues in product liability is timing. You must bring a claim within certain time limits or risk losing your right to recover.

• Under NH Rev. Stat. § 507‑D:2, a product liability claim must be filed within 3 years of when the injury is discovered (or reasonably should have been discovered).
• There are special rules if someone modified or altered the product. NH law bars liability for harm arising in any part from modification or alteration done by someone other than the manufacturer. However, courts have in some situations required that modification to be evaluated in relation to foresee-ability and the defendant’s responsibility.

Burden of Proof & Legal Theories

• Under strict liability, the injured party does not need to prove negligence: If the product was defective in manufacturing or design (or failed to warn), and that defect caused injury, the manufacturer or other responsible party may be liable. New Hampshire follows the Restatement (Second) approach in many respects.
• In design defect claims, as noted, the courts evaluate whether the design posed “unreasonable danger” by balancing risks vs. benefits. A plaintiff doesn’t necessarily need to prove that there was an alternative design (i.e. a safer substitute design) under some versions of NH law.
• Warnings/instructions must be adequate given what a user could reasonably foresee. If warnings are missing, unclear, or misleading, liability may follow. The manufacturer’s knowledge of risk and the foresee-ability of misuse are important.

Defenses & Limitations

• Alteration or modification of the product: If the product was later modified by someone else, and that alteration contributes to the injury, the manufacturer or seller can have a defense. NH law treats modification or alteration as a potential bar to liability.
• Foreseeability of misuse: If the way the product was misused was foreseeable to the manufacturer, the plaintiff may still recover; but if not, that can be a barrier. This is especially relevant when the defendant argues misuse or abnormal use.
• Statutory limitations (see above). If you wait too long after discovering injury—or after the product was sold—you may be barred.

Recent Legal Developments

One of the more notable recent developments in New Hampshire is the enactment of a law (House Bill 551, signed May 23, 2025) that limits product liability for firearms manufacturers with respect to certain design features. Under this law, firearm manufacturers (and federal licensees) are not liable in product liability lawsuits for the absence or presence of specific gun safety mechanisms (for example, certain external mechanical safeties) for guns sold in the state. However, the law still allows for claims based on manufacturing defects.

This change has significant implications, especially with ongoing litigation involving Sig Sauer and its P320 pistol, which plaintiffs have alleged discharges or safety problems related to design features.

What to Do If You Think You Have a Claim

If you believe you’ve been harmed by a defective product in NH:

1. Preserve the product: Keep the product (and its packaging, instructions, warnings). Photograph it; keep evidence of how you were using it.
2. Seek medical attention: Have care for your injury and collect medical records; they will be key.
3. Document everything: When did you first notice injury, what was the defect, how did you use the product, and did you modify or alter it in any way.
4. Consult a lawyer experienced in product liability: Product liability involves technical issues (design, warnings, manufacturing) and strict time limits. A lawyer can evaluate whether your case meets the legal standards and whether the statute of limitations or repose might bar your claim.

Conclusion

Product liability law in New Hampshire gives injured persons multiple legal routes to recover for injuries caused by dangerous or defective products. The law is governed by statute (RSA 507‑D) and refined by case law, providing definitions, time limits, and boundaries. But recent reforms—especially around firearms liability—show that the legal landscape is still evolving. If you think you have a claim, acting sooner rather than later is essential, given strict deadlines and potential defenses. Contact the experienced attorneys at PMM law today.