In Federal Court, When Is An Affidavit A Declaration Even if Not Notarized?

Time and again,  litigators experience hassles with a witness obtaining notarization of a signature. That sometimes leads to submission of affidavits that are technically not proper, and related angst. But is such an affidavit a declaration under penalty of perjury, if the “penalty of perjury” language is used?  Yes, said an Illinois federal court  See Snyder v. Wal-Mart Stores, No. 18 C 583 (April 2, 2018). Hat tip to Steven Garmisa for flagging the case in a July 16, 2018 article in the Chicago Daily Law Bulletin (paywall).