## Facts

- Aristocrat owned U.S. Patent No. 6,093,102, directed to an electronic slot machine that lets a player select winning symbol-position combinations on a multi-reel display.
- Aristocrat sued IGT in the District of Nevada, alleging IGT’s gaming machines infringed the patent.
- The asserted claims used means-plus-function language, including “game control means” and “control means,” implemented by a computer.
- The specification identified a general-purpose microprocessor executing “appropriate programming,” but did not set out the steps (e.g., flowchart or written logic) by which the computer performed the claimed functions.

## Issues

1. For a computer-implemented means-plus-function limitation under 35 U.S.C. § 112 ¶ 6, is disclosure of a general-purpose microprocessor with “appropriate programming” sufficient corresponding structure, or must the specification disclose an algorithm?
2. If the specification does not disclose the algorithm for the claimed function, are the claims indefinite under 35 U.S.C. § 112 ¶ 2?

## Decision

- The Federal Circuit affirmed summary judgment that all claims were invalid for indefiniteness.
- For computer-implemented means-plus-function limitations, the corresponding “structure” must include the algorithm that performs the claimed function; a general-purpose microprocessor plus “appropriate programming” is not enough.
- Because the patent failed to disclose any algorithm for the “game control means”/“control means” functions, the claims lacked corresponding structure and were indefinite.
- The parties agreed the claims “rise and fall together,” so the court’s analysis of an independent claim controlled invalidity of all asserted claims.

## Legal Principles

- Under § 112 ¶ 6, a means-plus-function limitation covers only the corresponding structure disclosed in the specification (and equivalents); for software-implemented functions, that structure is the disclosed algorithm executed by the computer.
- Disclosing only a general-purpose computer or microprocessor, without an algorithm describing how the function is performed, is treated as disclosing no corresponding structure for a computer-implemented means-plus-function element.
- When a means-plus-function claim lacks disclosed corresponding structure, the claim fails § 112 ¶ 2’s definiteness requirement and is invalid.

## Conclusion

The Federal Circuit held that computer-implemented means-plus-function claims require disclosure of an algorithm as corresponding structure; absent that disclosure, the functional claim language is indefinite and the claims are invalid.


Aristocrat Techs. Austl. Pty Ltd. v. Int’l Game Tech., 521 F.3d 1328 (Fed. Cir. 2008)