No. 95-728October Term 1996Decided Mar 31, 1997Updated Mar 3, 1997
Warner-Jenkinson v. Hilton Davis Chemical
Warner-Jenkinson Co. v. Hilton Davis Chemical Co.
Two chemical companies disputed whether a new dye purification process operating at a slightly different pH level infringed on an existing patent.
Case status
Decided 9-0 · March 31, 1997 · Opinion by Justice Thomas
Majority
- Rehnquist
- Stevens
- O'Connor
- Scalia
- Kennedy
- Souter
- Thomas
- Breyer
- Ginsburg
- Current stage
- Decided
- Latest event
- Decision released Mar 31, 1997
- What it's about
Two chemical companies disputed whether a new dye purification process operating at a slightly different pH level infringed on an existing patent. The Supreme Court upheld the 'doctrine of equivalents' to determine patent infringement, but remanded the case because the lower court did not apply all of the doctrine's requirements.
Question presented
Is the "doctrine of equivalents" a legitimate test for determining how similar a new invention must be to an existing patent to be deemed an illegal infringement?
- Case path
Decision released Mar 31, 1997
- Area
Decided Supreme Court case
Timing
Decided March 31, 1997
The Court released its decision on March 31, 1997 without hearing oral argument.
Documents
Opinions
Thomas, Ginsburg, Kennedy
Related cases
Grounding
- Grounding
- Primary-source trail available.
- Note
- Plain-English explainer. Official filings and opinions remain authoritative.
- Checked
- Jul 25, 2026
- Method
- Methodology