How does the examiner determine if species are patentably distinct?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Examiners determine if species are patentably distinct by evaluating their unique characteristics and search burden. The MPEP 809.02(a) states:

“In making a requirement for restriction in an application claiming plural species, the examiner should group together species considered clearly unpatentable over each other.”

Examiners assess whether:

• The species have mutually exclusive characteristics
• The species are not obvious variants of each other
• Searching for one species does not likely result in finding art pertinent to the other species

If these criteria are met, the species are considered patentably distinct, warranting a restriction requirement.