Preliminary injunction: what the decision maker looks at
A court asked to grant a preliminary injunction in a patent dispute checks four things in sequence: how strong the infringement claim looks on the papers, whether the patent is likely to survive a validity challenge, how much delay has already cost the applicant, and whether an interim order would cause disproportionate harm to the other side. A weak showing on any single point can sink the whole application, regardless of how strong the rest looks.
What changes once you file
Filing starts a formal clock. From that point, the record is fixed: whatever evidence, dates and arguments you submit is what the decision maker works with, and gaps are rarely allowed to be filled later. The other side typically gets a chance to respond before a decision is made, unless the applicant asks for and justifies an ex parte order. Urgency is judged against how long you took to act after you first learned of the infringement — a long, unexplained delay works against the applicant, whatever the underlying merits.
Factors the decision maker weighs
| Factor | What it shows | Typical evidence |
|---|---|---|
| Strength of infringement claim | How persuasive the technical comparison is | Claim charts, product samples, expert opinion |
| Validity risk | Whether the patent is likely to survive challenge | Prior art search, freedom-to-operate opinion |
| Urgency | Whether delay undermines the request | Dated correspondence, discovery timeline |
| Balance of harm | Who loses more if the order turns out wrong | Financial statements, market share data |
| Security offered | Whether the applicant can cover the other side's loss | Bank guarantee, escrow confirmation |
What to do before filing
- Instruct a patent attorney to prepare a claim chart comparing the patent against the accused product.
- Order a validity check on the patent before relying on it; a court will ask the same question.
- Record, in writing, exactly when you discovered the infringement — this date drives the urgency assessment.
- Prepare a security offer: a bank guarantee or escrowed sum to cover the other side's loss if the order later proves wrong.
- Decide, with counsel, whether to request an inter partes hearing or an urgent ex parte order.
- File with the competent court and ask, explicitly, for an expedited timetable.
Who decides, where, and how fast
The decision sits with the competent national court, or, where the patent is a unitary one, with the Unified Patent Court. A single judge or a small panel handles interim relief; full trial-style hearings do not happen at this stage. In practice, urgent requests are decided within days to a few weeks, faster where the applicant can show that any delay causes irreversible harm.
If your situation differs
If the evidence you need sits with a third-party design or engineering agency rather than with you, check who actually holds the underlying files before you file — ownership of the file is a separate question from ownership of the patent. Photonics and instrumentation an agency keeps the design files works through exactly this gap.
If the party you want to stop operates in tokenised or digital-asset markets, the downside of an order that turns out to be wrong is calculated differently, and the security you offer should reflect that. When enforcement is sought against a holder in detail sets out how that cost is worked out.
If the other side has already filed, or threatens to file, a nullity action against the same patent, expect the court to weigh validity risk more heavily and to move more cautiously on urgency.
What this page does not cover
This page describes the decision, not the price of getting there, and it does not predict an outcome for any specific patent. It also does not cover jurisdiction-specific filing formalities, which vary by court and change without much notice. For the wider scope of what the firm handles and where that scope stops, see About the firm and its scope and its limits.
Sources and limit
Procedural rules for interim relief are set by each competent court and published through its own rules of procedure and case-management guidance; they are not reproduced here because they vary by forum and change over time. This page was last reviewed for accuracy on 2024-06-01. Where the underlying dispute touches a supply chain rather than a single counterparty, the sequencing question looks different again — Counterparty report when a subprocessor is added in detail covers what to check first in that setting.
Related reading
A preliminary injunction is a step before, not instead of, the full case. Main infringement action step by step covers what happens once the interim phase ends.
FAQ
How long does a preliminary injunction take in practice?
Urgent requests are usually decided within days to a few weeks. The timeline depends on the forum, whether the request is ex parte, and how quickly the applicant can show that delay causes irreversible harm.
Which documents are needed to start?
At minimum: a claim chart comparing the patent to the accused product, evidence of when the infringement was discovered, a note on validity risk, and confirmation of the security the applicant can offer.
What happens if the other side does not respond?
Where the process allows an ex parte order, the court can decide on the applicant's submissions alone, subject to the respondent's right to challenge the order afterwards. Where a response is required, a non-response does not automatically favour the applicant; the court still tests the four factors on the record before it.