"An expert is someone called in at the last minute…

Entry in progress—B.P.

Google News Archive
27 August 1959, The Spokesman-Review (Spokane, WA), “Shop With Sue,” pg. 8, col. 6 ad:.
Colleague — Someone called in at the last minute to share the blame.

Google Books
The public speaker’s handbook of humor
By Helen Eisenberg and Larry Eisenberg
Grand Rapids, MI: Baker
1972, ©1967
Pg. 93:
Expert: Someone called in at the last minute to share the blame.

Google Books
Quote Unquote
By Lloyd Cory
Wheaton, IL: Victor Books
1977
Pg. 107:
An expert is someone called in at the last minute to share the blame.
(WISCONSIN JOURNAL OF EDUCATION)

GOogle Books
The Big Book of Business Quotations
By Editors Of Perseus Publishing, Basic Books
New York, NY: Basic Books
2003
Pg. 22:
An expert is someone called in at the last minute to share the blame.
Sam Ewing (1920-2001) U.S. author. Quoted in Reader’s Digest (December 1992)

“An expert is someone called in at the last minute to share the blame”