What is the three-prong test for identifying limitations under 35 U.S.C. 112(f)?

The three-prong test is used to determine whether a claim limitation invokes 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph. According to MPEP § 2181, the test consists of the following prongs:

1. The claim limitation uses the term “means” or “step” or a term used as a substitute for “means” that is a generic placeholder (also called a nonce term or a non-structural term having no specific structural meaning) for performing the claimed function;
2. The term “means” or “step” or the generic placeholder is modified by functional language, typically, but not always linked by the transition word “for” (e.g., “means for”) or another linking word or phrase, such as “configured to” or “so that”; and
3. The term “means” or “step” or the generic placeholder is not modified by sufficient structure, material, or acts for performing the claimed function.

If a claim limitation meets all three prongs, it is interpreted under 35 U.S.C. 112(f). The MPEP provides this guidance:

“As explained in MPEP § 2181, subsection I, claim limitations that meet the following three-prong test will be interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph.”

It’s important to note that the presence or absence of the word “means” creates a rebuttable presumption regarding the application of 35 U.S.C. 112(f). Examiners and practitioners should carefully apply this test to determine the proper claim interpretation.

To learn more:

• 35 U.S.C. 112(f)
• three-prong test
• means-plus-function
• claim interpretation