Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Not written by a barrister. The name was thought up by a second-year American law student sitting in a coffeehouse in Manhattan. Neither an authoritative statement of the law nor legal advice. Don't rely. Quick work.
Eighth Circuit: Compart's Boar Store, Inc. v. United States
FTCA
Scientific testing with ambiguous results that required expert interpretation qualifies for the discretionary function exception to federal liability under the FTCA.