I was reviewing an expired U.S. patent for a clever industrial process that is sufficiently dangerous that it should not be attempted by people not skilled in the art.

Throughout the patent, including in the descriptions of preferred embodiments and even in the claims, one of the essential ratios to the process given is almost 50% too low for it to work. I noticed this when I was preparing to test it. Thinking, "Well, it is patented, maybe there's something they know that I don't," I actually tried it as described in the patent. As expected, it failed harmlessly. Using the correct ratio the process succeeded beautifully.

Since this apparent error was repeated in multiple places, I tried unsuccessfully to locate one of the authors to ask if they had intentionally submitted an application with a value that would stymie someone not skilled in the art.

So: Is this a known practice? Is it common? Are there policies about doing this? Is it done by the request of the USPTO, or is it up to inventors to obfuscate dangerous inventions?

And what about the patent protection? In this case, the claims include an essential ratio that will not work. So if the patent were in force and I used the ratio that does work technically I wouldn't be infringing. Is this something that would be overlooked in litigation? E.g., would a court accept an inventor's argument that, "We all know the listed ratio is wrong, and I submitted it that way so anybody who should not be using this invention wouldn't end up injured or killed. But this defendant is clearly infringing my invention." Has such a claim ever been made and sustained?

1 Answer 1


Originally, there was a requirement that the inventor teach the best mode (that the inventor knows about) in the specification. In recent years, that requirement has been a bit relaxed, but it still is in effect.

Personally, I don't like obfuscation. If the patent obfuscates too much, it can potentially be rejected or invalidated as not being enabling under 35 USC 112. So this is one of the dangers of obfuscation.

Also, if the patent is teaching away from the ratio or approach that does work, you actually may be able to file (and get) your own patent claiming the correct approach. You can actually cite the patent with the wrong ratio as prior art, and explain that the prior art is teaching away from the correct result.

Unfortunately, I am not aware of any rules about discussing dangerous topics.

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