Q: For US patent law, if you make an item that you've never seen a patent law for, is it illegal?

A: Your question in a general sense is does it matter whether or not you have seen a patent for an idea before you start selling a product covered by that patent.

The answer is that you are liable for patent infringement to the owner of the earlier, unexpired patent whether or not you had seen that patent.

This is sometimes called the innocent infringer. You invented an idea and were not copying something but you had the bad luck of being the second person to invent. This is a big difference between patents and copyrights as a copyright owner has to show that you copied rather than independently developed your product.

That is why companies ask a patent attorney to do a freedom-to-operate search (sometimes called a clearance search) to reduce the risk that there is a patent that applies to the product they want to sell. A freedom-to-operate search reduces the risk of a patent problem but cannot drive that risk to zero as some patent applications which are patent pending are not visible during the search and may emerge to become problems later.

You may think this is unfair and that people that made a product knowing that there was a patent should be treated differently than the innocent infringer. The answer is that they can be punished more heavily. A judge can amplify the damages by a factor as high as 3x if a person knew of a patent and disregarded the patent. This is called willful infringement. (It can be excused if the person sought legal advice and relied on that advice that the patent claims did not cover the new product or that the relevant patent claims were invalid).

Kevin E Flynn