I lead the US practice group at a German patent firm, which means my actual job — underneath the office actions and the docketing deadlines — is translation. Not English to German; my colleagues' English is excellent and my German is a work in progress. The translation that matters is between two legal systems that look similar from a distance and turn out to have profoundly different instincts up close.

Nothing illustrates that better than the duty of disclosure.

"You want us to volunteer this?"

US practice imposes a duty of candor on everyone substantively involved in prosecuting a patent application — codified at 37 CFR 1.56. If you know of information material to patentability, you disclose it to the examiner. In practice that means filing Information Disclosure Statements citing the prior art you're aware of, very much including the art that a European or Japanese patent office just used against your own parallel application.

European clients hearing this for the first time tend to react somewhere between puzzlement and quiet alarm. The EPO has nothing with this shape — there are obligations to report certain search results when the office asks, but no continuing, personal duty to hand the examiner the best ammunition you know of against your own case. The instinctive response is always the same: why would we volunteer that?

The answer is that the American system enforces the duty with a weapon the European system doesn't have: inequitable conduct. A US patent procured by deliberately withholding material information can be held unenforceable — not the affected claims, the entire patent, and sometimes its relatives. The Federal Circuit tightened the standard in Therasense (it now takes but-for materiality and specific intent to deceive), which killed off the worst of the "plague" of boilerplate inequitable-conduct defenses. But the doctrine is alive, and the practical advice hasn't changed: when in doubt, disclose. A reference the examiner considered and moved past is spent ammunition. The same reference discovered in litigation, undisclosed, is a problem money can't always fix.

So a real part of my week is making sure everything of substance from the EP, JP, and CN files flows into the US file — a discipline that feels like paranoia to clients from systems where prosecution is more adversarial and less confessional. It isn't paranoia. It's the cheapest insurance in American patent law.

Other things that don't survive the crossing

The duty of disclosure is the sharpest example, but the list is long.

Examiner interviews. US examiners will get on the phone with you, informally, and it is often the single most productive hour in a prosecution. Clients calibrated to the EPO — where the comparable event is a formal oral proceeding you prepare for like a court date — chronically underuse this. I spend a surprising amount of energy talking clients into a conversation that costs almost nothing and regularly saves a round of prosecution.

Claim style. A claim drafted for European two-part form, with its "characterized in that" hinge, is a perfectly good EPO claim and an awkward US one. Going the other way, casually writing "means for" in a US claim can quietly invoke means-plus-function treatment under §112(f) and shrink your scope to the disclosed structures. None of this is exotic knowledge, but it's exactly the kind of thing that goes wrong when one office's habits are applied in the other's jurisdiction on autopilot.

The clock. Munich is six hours ahead of the East Coast, and I've come to like the asymmetry. Mornings here are quiet — the USPTO is asleep, nothing new can arrive, and drafting gets done. At 2:30 in the afternoon, America opens. The occasional late call to Pittsburgh is the tax; the protected mornings are the dividend.

The general lesson

None of these differences is a secret. They're all documented, and any competent practitioner can recite them. What I've learned working the seam between the systems is that the failure mode isn't ignorance — it's instinct. People prosecute the way their home system trained them to, and the habits are invisible until they collide with a rule that was never written down at home.

Which is, I suspect, a special case of something broader: expertise is mostly knowing which of your instincts don't travel. My German teacher would probably say the same about prepositions.