Earlier quoted context omitted.
It's completely different. For starters, there's the "reasonable person" test. No reasonable person is going to think that murder is legal. Intentionally infringing a patent is punished much more harshly, and it's impossible to keep up with the millions of patents that are published, so being intentionally unaware is actually a decent legal defence. And yes, this does mean that patents are generally pretty useless fo…
Also, I'm not a lawyer, so correct me if I'm wrong, but isn't it also patent infringement if the following happens: A patent is filed for technique X by company A, Company B use technique X having created it independently, The patent is issued to Company A, Company B is now infringing upon Company A's patent. Company B could not possibly have committed patent infringement intentionally, because the patent they infrin…
I don't know about the US situation but in the UK Section 64 of the Patents Act (http://www.ipo.gov.uk/pro-types/pro-patent/p-law/p-manual/p-... and http://www.legislation.gov.uk/ukpga/1977/37/section/64) allows a person to continue activity which was started prior to the grant of a patent in secret or where sufficient preparations for that [infringing] activity were made prior to the application/grant in good faith. If the activity wasn't in secret then it forms part of the prior art and invalidates, or forces amendment of, the patent in question.
If there isn't an equivalent US clause I'd be surprised: 35 U.S.C. 273 "Defense to infringement based on earlier inventor." looks like a candidate.