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AIPPI 2022: Beware of estoppel when amending claims

Ali Razai explains prosecution history estoppel in the US

Speakers at three firms explored how the US, China and European countries approached patent litigation estoppel

Applicants need to consider whether claim amendments would prevent them from raising doctrine of equivalents arguments in litigation, said speakers at AIPPI’s World Congress yesterday, September 12, in San Francisco.

Lawyers at the panel titled Mind your Words: Filewrapper Estoppel Role in Prosecution and Enforcement delved into the nuances of prosecution history estoppel in the US, Europe and China.

The doctrine of equivalents dictates that defendants can be held liable for infringement even when their products don’t literally infringe all limitations of patent claims.

But patentees couldn’t use this doctrine to recapture subject matter that they gave up during prosecution, said speakers.

Ali Razai, partner at Knobbe Martens in California, noted that the intent of the patent owner wasn’t relevant when determining estoppel.

Rather, parties should consider whether competitors looking at the prosecution history would believe patent owners had given up certain material.

He noted that this approach made sense because companies could invest a lot of money on the basis that they had freedom to operate.

“There are fundamental fairness issues at play,” he said.

There were two big factors that could lead to estoppel in the US, added Razai.

Claim amendments were one. If an applicant narrowed a claim after the USPTO said the scope was too broad, it couldn’t then use the doctrine of equivalents to assert the patent under the given-up scope, he said.

Argument-based estoppel was the other. This factor would apply if an applicant made a clear and unmistakable argument to an examiner that the patent didn’t include certain material. In such a case, said filer couldn’t later argue that the patent did include that material.

Applicants’ prosecution histories in other jurisdictions wouldn’t lead to estoppel in the US, however, said Razai.

But he pointed out that judges would likely be aware of the evidence, which could shape their views of cases.

“Judges are human,” he said.

EU patchwork

Applicants prosecuting in Europe should familiarise themselves with the nuances of each jurisdiction, said panellists.

Daan de Lange, partner at Brinkhof in the Netherlands, pointed out that the European Patent Convention didn’t mention prosecution history, so patentees in the region couldn’t rely on a single approach.

He highlighted that a few different European jurisdictions had looked at whether and when prosecution history could work against plaintiffs.

The Netherlands gave alleged infringers liberty to raise whatever arguments they wanted, he said.

He added that German courts took a similar approach, setting out that it was permissible for defendants to use statements made by applicants, but that said statements shouldn’t be the sole basis for claim construction.

It will be interesting to see how the issue plays out at the UPC, said de Lange. He noted that AIPPI had held a mock UPC trial with European judges earlier in the day.

A litigator had raised an argument based on prosecution history, and the mock judges accepted the party’s right to raise it.

Applicants should also be wary about what they say when prosecuting their patents in China.

Chinese law dictates that patentees can’t recapture technical solutions surrendered during patent prosecution in infringement proceedings, said Guoxu Yang, director of the Silicon Valley Office of the CCPIT Patent and Trademark Law Office.

Practical solutions

Speakers also discussed how applicants could avoid estoppel.

Razai at Knobbe said counsel could do some damage control if they had to amend their claims knowing that estoppel would kick in. Prosecutors could try to go on the record and emphasise that they disagreed with examiners but had amended claims to expedite the process, he said.

They wouldn’t likely win disputes on this basis. But they could force the opposing parties to spend more time on their cases, which could help them procure more favourable settlements, Razai added.

Isabelle Chabot, director of patents at telecoms company EXFO in Canada, moderated the talk.

AIPPI is taking place this week at the Marriott Marquis in San Francisco.

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