You don't need convincing proof, just reasonable suspicion to file a lawsuit. (There's something called Rule 11 to discourage frivolous lawsuits, but it's a pre

You don't need convincing proof, just reasonable suspicion to file a lawsuit. (There's something called Rule 11 to discourage frivolous lawsuits, but it's a pretty low bar.) You can then determine actual infringement during discovery. This has some problems however: 1) As you can imagine discovery may not turn up any actual infringement, making it all a huge, expensive waste of time. 2) The unfortunate reality of patent lawsuits is that if you can't prove infringement just by looking at something, you might as well have already lost. Anything that requires expert witnesses to provide input on often comes down to which sides' witness the jury finds more likable, and that's pretty much a roll of the dice.