## Facts

- Jack McMahon bought coffee at a Mobil station and drank it while driving.
- Angelina McMahon removed the lid and attempted to pour coffee into a smaller cup; coffee spilled onto her lap, causing second- and third-degree burns and scarring.
- Angelina attributed the spill to a collapsing Styrofoam cup; the McMahons settled with the cup and lid manufacturers before appeal.
- The remaining defendant manufactured the commercial coffee maker used to brew and hold the coffee.
- The machine brewed coffee at about 195°F and held it at about 179°F on a hotplate.
- The McMahons alleged (1) failure to warn more specifically about the severity of burn injuries and (2) defective design because the machine produced coffee “too hot for human consumption.”
- Both plaintiffs admitted they knew hot coffee can burn and that they wanted coffee served hot.
- The district court granted summary judgment to the manufacturer; the plaintiffs appealed.

## Issues

1. Whether a manufacturer must warn consumers in detail about the severity of burn injuries from hot coffee beyond the commonly known risk that hot coffee can burn.
2. Whether brewing and holding coffee at approximately 195°F/179°F makes the product unreasonably dangerous or defectively designed under Indiana product liability law.
3. Whether the plaintiffs presented admissible expert evidence sufficient to create a triable issue on defect or unreasonable danger.

## Decision

- The Seventh Circuit affirmed summary judgment for the manufacturer.
- The failure-to-warn claim failed because the risk that hot coffee can burn is obvious and commonly understood, and the law does not require detailed warnings cataloging degrees of injury.
- The design-defect claim failed because the challenged temperatures were consistent with ordinary consumer expectations and industry practice, and the product’s function depends on serving coffee hot.
- The plaintiffs’ expert affidavit was excluded as methodologically unsupported; without it, the record lacked evidence of defect, unreasonable danger, or a required safer alternative.

## Legal Principles

- Manufacturers generally have no duty to warn about dangers that are open and obvious or matters of common knowledge to ordinary consumers.
- Warnings need not provide exhaustive detail about the magnitude of a commonly known risk; excessive warning detail may be counterproductive.
- A product is not defective merely because it can cause injury; inherent risks tied to an intended and desired function do not alone establish unreasonable danger.
- On summary judgment in a product case, plaintiffs must present admissible expert testimony when technical causation or defect claims depend on specialized knowledge; conclusory or unsupported expert opinions are inadmissible.

## Conclusion

The court held that hot coffee’s burn risk is a matter of common knowledge, that industry-standard brewing and holding temperatures did not render the coffee maker unreasonably dangerous, and that the plaintiffs’ unsupported expert evidence could not create a triable defect or warning issue; summary judgment for the manufacturer was affirmed.


McMahon v. Bunn-O-Matic Corp., 150 F.3d 651 (7th Cir. 1998)