In a products liability case, a "design defect" is a problem or condition a product has that causes injury to someone who uses the product. A design defect is a problem with the product's design that makes the product inherently dangerous. This is even if it is manufactured perfectly and made of the best-quality materials.
A design defect is not to be confused with a manufacturing defect. A manufacturing defect refers to when a product is not made in accordance with the blueprints, plans or specs. To help illustrate the difference, let's look at two examples:
Karla purchased an SUV. The make of the SUV made it so that the SUV has a tendency to roll over when its driver needs to swerve to avoid an object or other hazards. This would be a design defect.
Let's change the facts. Karla purchased an SUV. This particular SUV was not made according to the blueprints, making it so that this SUV has a tendency to roll over when its driver needs to swerve to avoid an object or other hazards. This would be a manufacturing defect.
Another example of a design defect can be seen in the Trinity ET-Plus System guardrails. When the manufacturers improperly redesigned the ET-Plus System, the change in the width of the guardrail made the product unreasonably dangerous, causing the guardrail to act like a spear rather than a buffer. The defect would be considered a design rather than a manufacturing defect, because all the guardrails were made in accordance with a new blueprint. Because of this change, hundreds have been injured and some have even died. This real-life example goes to show you how dangerous altering a design can be; an alteration could cause the product to become deadly.