A design defect is one of the ways to prove your product liability case. This is one of the three defects you may find in products.
You will want to be sure that you have a product with an actual defect in the design before you use this angle in your case.
According to Cornell Law School, a design defect is one that occurs in the initial stages of product development. It is dangerous regardless of how you manufacture it or market it. The product is naturally hazardous because of errors made when the company designed it.
To prove there is a design defect, you will have to show the defect would exist no matter what else happens. For example, you want to show that there was nothing in the manufacturing process that could have changed the product to no longer be defective because the issue was in the blueprint of the product.
You also can show the defect exists in all the products in this product line. A design defect will not just impact the product you bought. Every single product sold that used the same design will have the issue.
Finally, you need to show there is an alternative design the company could have used that would eliminate the defect and the danger associated with the product. This alternative design must allow the product to still function the same and be essentially exactly like the defective product but without the hazard.
Proving a design defect can be tricky because you need to ensure issues did not occur elsewhere in the manufacturing or sales process.