4 ms·

Say it's expired early for not paying fees. Still hard to know what the actual legal state is. The site lists them by filing grant date plus 20 years, which is

• derf_ 10y ago
  It's really hard to know when a patent will expire or has expired. Figuring out the relevant priority date is complicated, especially when foreign applications are involved. We're still in the region where you have to worry about the June 8, 1995 rules change. Patents whose prosecution took an unusually long amount of time can still be granted a term extension. Re-issued patents can complicate things even more. I've known patent attorneys who will consult with another lawyer more well-versed in the intricacies involved rather than trust their own ability to figure it all out. I've seen the legal status listed on http://portal.uspto.gov/pair/PublicPair http://portal.uspto.gov/pair/PublicPair be literally years out of date, and I don't know of any way to ask the US PTO if a given patent is expired. I was hoping this site had figured out something I didn't know. When it matters, make sure to consult your lawyer.