Patent troll is a label, not a legal category, and the label does a lot of work that the facts sometimes do not support.
The neutral term is non-practising entity. An owner that does not make or sell anything covered by its patents.
Which immediately catches universities, research institutes, failed companies and individual inventors — few of whom anyone calls trolls. The label describes conduct people object to rather than a structural fact about the owner.
What the objection actually targets is cost asymmetry. A demand priced below the cost of defending is designed to be paid whether or not it has merit, and that is the practice the term was coined for.
Who does not practise their patents
| Owner type | Practises? | Called a troll? |
|---|---|---|
| Universities | No | Almost never |
| Research institutes | No | Rarely |
| Individual inventors | Usually not | Rarely |
| Failed companies' successors | No | Sometimes |
| Defensive aggregators | No | No |
| Assertion entities | No | Usually |
| Operating companies asserting non-core patents | Partially | Sometimes |
The structural fact is identical across every row. What differs is the behaviour: whether the assertion is grounded in analysis, priced against merit, and directed at a genuine infringement.
Which is why the useful question about any letter is not who sent it, but whether the claims read on your product.
The business model
| Step | What happens |
|---|---|
| Acquire | Patents bought cheaply, often from failed companies or lapsing owners |
| Identify targets | Products that plausibly read on the claims |
| Demand | Letters at a price below defence cost |
| Settle | Most recipients pay |
| Litigate | A minority, to sustain credibility |
Acquisition is cheap because the sellers have no alternative. A company winding down, or an owner facing a maintenance fee they cannot justify, sells for a fraction of what an assertion campaign might yield.
Nearly three in five US utility patents are abandoned before term — see the patent survival curve — and that pool of unwanted patents is where assertion portfolios come from.
Pricing below defence cost is the mechanism. A demand at a level clearly below what litigation would cost makes settlement the rational choice independently of merit, which is precisely the objection.
Why defending costs so much
| Burden | Falls on |
|---|---|
| Source code production | You |
| Sales and financial records | You |
| Engineer depositions | You |
| Document preservation | You |
| Business disruption | You |
| Producing a patent and an assignment | Them |
The asymmetry is structural, not tactical. An operating company holds everything discoverable; an assertion entity holds almost nothing.
Which is why settlement pressure exists regardless of the patent's strength, and why the practice attracts the criticism it does. See patent litigation.
Where assertion portfolios come from
| Source | Why patents become available |
|---|---|
| Failed companies | Assets sold in wind-down |
| Owners facing maintenance fees | The fee exceeds perceived value |
| Individual inventors | No means to enforce alone |
| Corporate portfolio pruning | Non-core patents released |
| Bankruptcy estates | Liquidation |
| Universities | Licensing mandate, no enforcement capacity |
The maintenance fee window is the main supply mechanism. An owner facing $8,280 on a patent generating nothing will take a fraction of that from a buyer, because the alternative is receiving nothing at all.
Which means assertion entities buy at the exact moment owners are least able to negotiate. See patent portfolio pruning.
It also means some acquired patents are genuinely strong. A failed company's patents may cover technology the market later adopted, which is a real asset regardless of who ends up holding it.
Reading a demand letter
| The letter | What it signals |
|---|---|
| Identifies specific claims | Someone did analysis |
| Includes a claim chart | Serious |
| Names the accused feature precisely | Serious |
| Refers vaguely to "your products" | Screening exercise |
| Cites a patent without a number | Not credible |
| Demands a response in days | Pressure tactic |
| Offers a low flat licence to many parties | Volume campaign |
A letter with no claim chart has usually not been analysed against your product. That does not make it safe to ignore, but it changes what you are dealing with.
Volume campaigns are identifiable. A modest flat fee, a short deadline and generic accusation language indicate a letter sent to many recipients rather than a considered assertion against you.
The first day's work
| Step | Time | Why |
|---|---|---|
| 1. Confirm the patent is in force | 5 min | It may have lapsed |
| 2. Check current ownership | 10 min | The sender must own it |
| 3. Read the independent claims | 30 min | Letters overstate scope routinely |
| 4. Compare element by element | 2 hours | The all-elements rule |
| 5. Read the prosecution history | 1 hour | Narrowing limits construction |
| 6. Check for pending continuations | 15 min | Wider exposure |
| 7. Preliminary prior art search | 2 hours | IPR viability |
Do all seven before responding. They take a day and they frequently reveal that the claims are narrower than asserted, that the patent lapsed, or that the sender does not own it.
Ownership is worth checking specifically. The front-page assignee reflects grant only, and assertion entities frequently hold patents through shell entities whose chain of title has gaps. See patent assignment database.
Response options, by cost
| Option | Relative cost | When it fits |
|---|---|---|
| Ignore | Nil | Only for clearly non-credible letters, and rarely |
| Request a claim chart | Nil | Always reasonable; tests seriousness |
| Design around | Engineering time | The claim covers a changeable detail |
| Negotiate a licence | Low | The claims read and the price is sensible |
| IPR petition | Moderate | You have strong documentary prior art |
| Declaratory judgment | High | You need the uncertainty resolved |
| Full defence | Highest | Everything else failed |
Requesting a claim chart costs nothing and is informative. A sender with analysis will provide one; a volume campaign frequently will not.
Design-around remains the cheapest genuine resolution. If the claim recites a detail you can change, changing it ends the exposure without paying anyone.
Volume campaigns versus targeted assertions
| Volume campaign | Targeted assertion | |
|---|---|---|
| Recipients | Many | Few |
| Demand size | Below defence cost | Substantial |
| Claim chart | Usually absent | Present |
| Product identified | Generically | Specifically |
| Deadline | Short | Reasonable |
| Willingness to litigate | Low | Real |
| Right response | Analyse, then respond briefly | Full analysis and strategy |
A volume campaign is priced to be paid rather than fought, and identifying one changes the response. The analysis is the same; the escalation path is not.
Targeted assertions deserve the full treatment. Claim chart, prior art search, prosecution history, design-around costing and an opinion.
Both start with the same first day of work, which is why doing that work before responding matters regardless of which you have received.
The IPR route
| District court | Inter partes review | |
|---|---|---|
| Invalidity standard | Clear and convincing | Preponderance |
| Grounds | Any | §102/§103 on documents only |
| Cost | Seven figures | Substantially less |
| Timeline | 2–4 years | ~18 months |
| Filing deadline | — | 1 year from service |
| Estoppel | — | Grounds raised or reasonably could have been |
The preponderance standard is the reason IPR matters. The same prior art that would fail against a presumption of validity in court can succeed before the Board.
The one-year bar is absolute and starts on service of a complaint. Missing it forfeits the route.
Institution is discretionary and has been volatile — roughly 65% in October 2024, falling to around 37% by February 2026. Quote that with its date. See inter partes review.
What changed after the AIA
| Change | Effect |
|---|---|
| Inter partes review created | Cheaper validity challenges |
| Joinder restricted | Fewer mass multi-defendant suits |
| False marking claims narrowed | Ended one abuse category |
| TC Heartland on venue | Constrained forum selection |
| Octane Fitness on fees | Fee shifting more attainable |
| Alice on eligibility | Many software patents invalidated |
Several of these together changed the economics substantially. Cheaper validity challenges plus constrained venue plus more available fee shifting altered what a marginal assertion is worth.
Fee shifting
Available, and not routine.
| Statute | 35 U.S.C. 285 |
| Standard | Exceptional cases |
| Test | Octane Fitness — totality of circumstances |
| Practical effect | More attainable than pre-2014, still uncommon |
| Requirement | Litigating to the end rather than settling |
Pursuing fees means not settling, which is the tension. The cases where fee shifting is most deserved are frequently the ones a defendant most wants to end cheaply.
It does shape behaviour at the margin, because a plainly meritless campaign now carries a real risk that did not exist before Octane Fitness.
Joint defence and shared cost
Volume campaigns hit many companies with the same patent, which creates an opportunity.
| Mechanism | Benefit |
|---|---|
| Joint defence group | Shared prior art searching and costs |
| Shared IPR petition | One challenge, many beneficiaries |
| Common counsel | Reduced duplication |
| Information sharing | Others may already hold the killer reference |
| Defensive aggregator | Pooled acquisition and licences |
A single IPR can resolve a campaign against dozens of companies, because cancelling the claims removes the patent from everyone's problem at once.
Finding the other recipients is usually possible. Litigation dockets show who has been sued on the same patent, and that is a public record.
Reducing exposure
| Measure | Effect |
|---|---|
| Monitor your CPC classes | Advance warning of acquisitions and filings |
| Watch NPE litigation in your area | Who is asserting, against whom |
| Maintain defensive prior art | Ready material for any assertion |
| Keep FTO analysis current | Opinions age |
| Defensive aggregator membership | Pooled acquisition and licences |
| Publish defensively | Stops patents issuing at all |
Monitoring is the highest-value measure because assertion campaigns are visible before they reach you. An entity acquiring patents in your classification is telegraphing its next move. See patent monitoring.
Defensive publication prevents the patent existing. It is cheap, immediate, and the only measure that removes the problem rather than preparing for it. See can you patent something and make it free.
Worked example: two letters
Same week, two demand letters, very different responses.
| Letter A | Letter B | |
|---|---|---|
| Claim chart included | No | Yes, element by element |
| Accused feature named | "your software products" | A specific named module |
| Patent status | Lapsed 3 years ago | In force, second fee paid |
| Ownership | Recorded to a dissolved entity | Clean chain |
| Demand | Flat licence, low four figures | Negotiable, six figures |
| Deadline given | 10 days | 45 days |
Response to A
| Step | Outcome |
|---|---|
| Patent Center check | Expired for unpaid maintenance fee |
| Response | Short letter noting expiry |
| Cost | Under an hour |
| Result | No further contact |
The patent had lapsed and the letter was sent anyway. Ten minutes in Patent Center ended it.
Response to B
| Step | Outcome |
|---|---|
| Element-by-element comparison | Three of four elements present |
| Fourth element | Arguably present under equivalents |
| Prosecution history | Claim narrowed to overcome prior art — estoppel likely |
| Prior art search | Two strong references, both documents |
| Assessment | Real exposure, but IPR viable |
| Action | Opinion obtained; IPR prepared; negotiation opened from a position |
Letter B was a genuine assertion and was handled as one. The estoppel finding and the prior art moved the negotiation substantially without litigation.
The difference between the two was found in a day, and the day cost less than either settlement.
What the label obscures
Some assertions by non-practising entities are meritorious, and treating the category as uniformly abusive causes real errors.
| Reality | Consequence of ignoring it |
|---|---|
| Patents from failed companies can be strong | Dismissing a valid claim |
| Individual inventors often cannot enforce alone | Assertion is their only route |
| University patents rely on licensing | The model funds research |
| Some campaigns are purely opportunistic | Paying claims that read on nothing |
The analysis is the same regardless of who sent the letter. Is the patent in force, do the claims read on the product, and is there prior art. Who owns it affects negotiation, not infringement.
Insurance and funding
| Mechanism | What it covers |
|---|---|
| IP defence insurance | Defence costs, sometimes settlements |
| Indemnity from suppliers | Claims arising from supplied components |
| Customer indemnity you gave | Your exposure to customers' claims |
| Litigation funding | Plaintiff-side, occasionally defence |
| Defensive aggregator membership | Pooled licences |
Indemnities you granted are the exposure people forget. A supply agreement promising to indemnify customers against IP claims means their demand letters become yours.
Check both directions at the outset. What you are owed by suppliers, and what you owe customers, determines who actually funds the response.
Patent trolls: the checklist
- Never settle before checking the patent is in force. Lapse ends the matter for nothing.
- Verify current ownership. The sender must own what they assert.
- Read the independent claims yourself. Letters routinely overstate scope.
- Compare element by element. One missing element defeats literal infringement.
- Request a claim chart if none was provided. It costs nothing and tests seriousness.
- Read the prosecution history for narrowing that estops equivalents.
- Diarise the one-year IPR bar from service of any complaint.
- Price the design-around before pricing the settlement.
- Get a written opinion if you are continuing with knowledge of the patent.
- Monitor your CPC classes. Campaigns are visible before they arrive, and advance warning is the cheapest defence available.