A product is in a defective condition, unreasonably dangerous to the user, when it has a propensity or tendency for causing physical harm beyond that which would be contemplated by the ordinary user, having ordinary knowledge of the product's characteristics commonly known to the foreseeable class of persons who would normally use the product.
With regard to the issue of 'legal cause,' a defective condition is a legal cause of injury if it directly and in natural and continuous sequence produces or contributes substantially to producing such injury, so that it can reasonably be said that, except for the defective condition, the injury complained of would not have occurred. A defective condition may be a legal cause of damage even though it operates in combination with the act of another, some natural cause, or some other cause if such other cause occurs at the same time as the defective condition and if the defective condition contributes substantially to producing such damage.
Thus, in cases involving allegedly defective, unreasonably dangerous products, the manufacturer may be liable even though you may find that it exercised all reasonable care in the design, manufacture and sale of the product in question.
On the other hand, any failure of a manufacturer of a product to adopt the most modern, or even a better safeguard, does not make the manufacturer legally liable to a person injured by that product. The manufacturer is not a guarantor that nobody will get hurt in using its product, and a product is not defective or unreasonably dangerous merely because it is possible to be injured while using it. There is no duty upon the manufacturer to produce a product that is 'accident-proof.' What the manufacturer is required to do is to make a product which is free from defective and unreasonably dangerous conditions.