Can examiners consider prior art not cited in the reexamination request?

Yes, examiners are not limited to the prior art cited in the reexamination request. According to MPEP 2244:

“The examiner is not limited in making the determination based on the patents and printed publications relied on in the request. The examiner can find ‘a substantial new question of patentability’ based upon the prior art patents or printed publications relied on in the request, a combination of the prior art relied on in the request and other prior art found elsewhere, or based entirely on different patents or printed publications.”

This gives examiners flexibility in considering a wide range of prior art when determining if a substantial new question of patentability exists.

To learn more:

Topics: MPEP 2200 - Citation Of Prior Art And Ex Parte Reexamination Of Patents, MPEP 2244 - Prior Art On Which The Determination Is Based In Requests Filed Under 35 U.S.C. 302, Patent Law, Patent Procedure
Tags: ex parte reexamination, Patent Examiner, Reexamination Request