Sometimes a rejection seems so plausible and reasonable, you immediately start to develop a retreat plan. This especially occurs where language in the MPEP makes it seem like the Examiner’s approach is fully supported by the case law. However, remember that the MPEP may not always be written to give all of the relevant information to a particular issue. Consider MPEP 2143 and rationale provided therein regarding the “Simple Substitution of One Known Element for Another To Obtain Predictable Results.” The MPEP explains that the examiner must make certain findings, but does not fully discuss the burden of providing evidence establishing these findings.

A recent PTAB decision (SN 13/480,053) illustrates how the Office must do more than just make findings. In that case, the issue was whether the substitution of one known element for a known equivalent had been properly established (internal citations omitted):

The Examiner correctly indicates that the substitution of one known element for a known equivalent is prima facie obvious. However, the Examiner fails to appreciate that the burden is on the Examiner to first provide evidence establishing that compounds are well-known equivalents/or a specific purpose. We agree with Appellants that the Examiner has failed to meet the initial burden to provide sufficient evidence to support a finding that one of ordinary skill in the art would have recognized that Jessop's and McGinnis's amine-based solvents are equivalents for the specific purpose of acting as single-phase draw solutions in a forward osmosis process. Therefore, because the Examiner's findings are insufficient to support a prima facie case of obviousness, we do not sustain the rejection of independent claim 1 or its dependent claims 2-7, 9, 13, 14, and 26-31. Nor do we sustain the rejection of independent claim 15 and its dependent claims 16-20, or the separate rejection of claims 11, 12, and 17, both of which are based on the same, unsupported finding that Jessop's and McGinnis's amine-based solvents are equivalents.

Thus, before the Office can establish a prima facie case, it must do more than simply find equivalence for purposes of substitution. And even if the Office does have some evidence to support the finding, the applicant is still able to make a rebuttal with further evidence, and the Office must at least consider that evidence. Returning to the above case, the PTAB also explains the issue of rebuttal (internal citations omitted and emphasis added):

For completeness, we add that even accepting the Examiner's findings as sufficient to satisfy the initial burden to show that the ordinary artisan would have recognized Jessop's and McGinnis's amine-based solvents as equivalents for use as single-phase draw solutions, we nevertheless would reverse the Examiner's decision to reject the claims due to the Examiner's failure to meaningfully address Appellants' rebuttal evidence. A finding of equivalence is a determination of fact. Proof can be made in any form; through the testimony of experts or others versed in the technology; by documents, including texts and treatises; and, of course, by the disclosure of the prior art. Like any other issue of fact, final determination requires a balancing of credibility, persuasiveness and weight of evidence. To rebut the Examiner's finding that Jessop's and McGinnis's amine-based solvents were known equivalents, Appellants provided evidence in the form of declaration testimony supported by numerous publications. The record is devoid of any indication that the Examiner considered the publications cited by Dr. Wilson. Moreover, the Examiner's comments suggest the Examiner, at best, conducted a cursory review of the declaration testimony and Appellants' arguments, and completely failed to consider the supporting evidence. Compare, e.g., Appeal Br. 21 ("Appellant notes that the suitability of the switchable hydrophilicity solvent of Jessop to effectuate phase change is not the issue precluding the switchable hydrophilicity compounds of Jessop from being obvious substitutes for the compounds taught by McGinnis in the process of McGinnis. Rather, Appellant asserts that the uncertainty precluding one of ordinary skill in the art from finding the switchable hydrophilicity compounds of Jessop to be obvious substitutes for the compounds of McGinnis is the ability of the switchable hydrophilicity compounds to function as draw solutes of a draw solution formulated to draw a solvent across a membrane through forward osmosis.") and id. at 22 ("Appellant is not arguing that the SHS solvents of Jessop are not capable of functioning as draw solutes in forward osmosis. Rather, Appellant is arguing that one of ordinary skill in the art at the time of the invention would not reasonably expect that the SHS solvents of Jessop would be able to successfully function as draw solutes in the forward osmosis process taught by McGinnis."), with Ans. 15 ("The applicant has not provided any reasons why SHS solvents of Jessop would not be capable of functioning as draw solutes in forward.)

This rebuttal evidence is not like overcoming a prima facie case with secondary considerations (which is very difficult, in general, before an examiner and/or the PTAB). Instead, this rebuttal evidence goes to the finding of whether the substitution of equivalent elements is correct.

In this case, the applicant provided specific evidence as to why one skilled in the art would not have a reasonable expectation that the substitution could be made, even though in the end, of course the substitution would work (because it was the claimed invention!).