CPCTemporary injunctionHouse of Lords (UK)

American Cyanamid Co. v Ethicon Ltd.

[1975] Appeal Cases 39619751 min read
The case in brief30-second read
Facts
American Cyanamid (patent holder) sought interlocutory injunction to restrain Ethicon from selling allegedly infringing absorbable surgical sutures. The trial court examined the merits in detail and refused the injunction, finding no prima facie case.
Issue
What is the correct approach for courts when considering interlocutory injunctions: should they resolve merits or only assess threshold viability?
Held
At interlocutory stage, the court should not try to resolve contested questions of fact or law.
Principle
At interlocutory stage, the court should not resolve contested questions of fact or law; it need only satisfy itself there is a serious question to be tried, then consider balance of convenience. Widely adopted in Indian courts alongside the Dalpat Kumar test.
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Facts

  • American Cyanamid (patent holder) sought interlocutory injunction to restrain Ethicon from selling allegedly infringing absorbable surgical sutures
  • The trial court examined the merits in detail and refused the injunction, finding no prima facie case
  • The matter reached the House of Lords on the proper approach to interlocutory injunctions

Issue

  1. What is the correct approach for courts when considering interlocutory injunctions: should they resolve merits or only assess threshold viability?

Held

  • At interlocutory stage, the court should not try to resolve contested questions of fact or law
  • The threshold is low: "serious question to be tried" (not probability of success)
  • Once the threshold is met, the court considers balance of convenience
  • The guiding principle is: which course carries the lesser risk of injustice if the court turns out to be wrong?
  • If damages would be an adequate remedy for the plaintiff, no injunction should be granted

Ratio decidendi

Interlocutory injunctions require only a "serious question to be tried" (not prima facie case in the strong sense). Beyond that threshold, balance of convenience determines the outcome.

Exam use

How to use it in an answer

- Key line: "In American Cyanamid (1975), the House of Lords held that at interlocutory stage, courts should not resolve merits. The threshold is 'serious question to be tried'; then balance of convenience decides. Indian courts apply this alongside Dalpat Kumar."

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Citation

American Cyanamid Co. v. Ethicon Ltd. [1975] Appeal Cases 396

Reported: [1975] AC 396. This is an educational summary, not the judgment itself. Cite the reported version in professional or academic work.