Do unintended features in patent drawings count as prior art?

Yes, unintended features shown in patent drawings can count as prior art. The MPEP 2125 clearly states:

“When the reference is a utility patent, it does not matter that the feature shown is unintended or unexplained in the specification. The drawings must be evaluated for what they reasonably disclose and suggest to one of ordinary skill in the art.”

This means that even if a feature in a drawing wasn’t explicitly described or intended by the original inventor, it can still be considered prior art if it would be reasonably understood by someone skilled in the field. This principle was established in the case of In re Aslanian, 590 F.2d 911, 200 USPQ 500 (CCPA 1979).

To learn more:

• prior art
• patent drawings
• unintended features
• utility patents
• In re Aslanian