You Received a Patent Infringement Warning Letter: What to Do First (and Where Design-Around Fits)

What this article is not

This is not a litigation guide and certainly not legal advice. Receiving a warning letter is a legal event, and its first responder can only be a practicing patent attorney. What this article covers: what not to get wrong before engaging counsel, and where the engineering team can genuinely help after.

The first 48 hours: three dos, three don'ts

Do

1. Preserve the letter and its envelope/email headers completely. The receipt date can matter later (notice timing, response deadlines).
2. Contact patent counsel immediately. Not "let's study it internally first" — the letter creates legal notice, and continued practice after receipt can, in some jurisdictions, support willfulness and enhanced damages. The earlier the assessment, the more options remain.
3. Control internal communications. Appoint a single point of contact; route discussions through counsel-guided channels. Casual remarks in everyday email and chat ("this feature really is like theirs") can become adverse evidence.

Don't

1. Don't reply with a position. Whether firm denial or conciliatory outreach, any written response should be drafted or reviewed by counsel first.
2. Don't rush a product change. Liability for sold units doesn't vanish with later changes, and panicked redesigns can read as admissions. Whether, how and when to change is a strategy question that follows counsel's assessment.
3. Don't discuss publicly. Social media, industry groups, customer-facing explanations — one voice, set by counsel.

What counsel does: turning assertions into facts

A warning letter is fundamentally the sender's assertion. Counsel's job is decomposing it into verifiable questions:

• Infringement mapping: does your product practice every element of the asserted claims (All-Elements Rule)? Many letters do not survive element-by-element comparison.
• Validity analysis: does prior art threaten the asserted patent? Asserted patents get invalidated in response with some regularity.
• Claim construction: is the sender reading its own claims too broadly? The specification and prosecution history often pull the scope back in.
• Procedure and strategy: respond, negotiate, license, invalidate, defend — costs and odds of each path.

No tool substitutes for this step. AI can assist counsel with the search-and-compare legwork; judgment and strategy remain the practitioner's domain.

Design-around's correct place: the next generation

The engineering team's most valuable contribution to the dispute is usually not on the current battlefield but in the next-generation product:

Once counsel's claim analysis is done, you know precisely where the asserted patent's boundary runs and which limitations are unavoidable. That is when to start the design-around — attack the weakest limitation with a different technical route, run the equivalents self-check, hand the survivors back to counsel — so the next product is born outside the asserted scope.

The strategic effects compound:

• Negotiating leverage: when the other side knows your next generation no longer depends on the disputed technology, the settlement and licensing calculus shifts — you are buying a transition period, not survival.
• Loss containment: even if the current dispute goes badly, the damage is bounded to existing inventory rather than mortgaging the company's future.
• Time value: design-around R&D takes a cycle, and dispute procedure takes a cycle — running the two timelines in parallel puts you a product generation ahead of waiting out the lawsuit first.

Conversely, wielding design-around as a fire extinguisher for the current dispute — "quick, change the design so they can't sue" — underestimates existing liability and overestimates the legal effect of rushed changes. A good tool in the wrong position works against you.

The order is the strategy

The full sequence: letter → counsel → fact analysis → strategy → (in parallel) next-gen design-around → formal FTO before launch.

Every step has an irreplaceable owner: legal moves belong to counsel, technical routes to R&D, and the tool's place is inside the R&D step — making direction screening cheap and the equivalents self-check rigorous. Getting the order right is worth more than being clever at any single point.