The "Lycoming Flyer" newsletter is a reasonably authoritive source of engine handling information. The last edition of Lycoming's "Key Reprints" 2002 made the following point under the heading of National Transportation Safety Board Warning on Simulated Engine-Out Maneuvers. .
The fatal crash of a light twin in which a flight instructor and an applicant for a multi-engine rating were killed prompted the NTSB to issue an urgent warning to all pilots simulating an engine-out condition on multiengine airplanes. The Board's investigation revealed that some flight instructors do use the fuel selector or the mixture control to shut down an engine to test a multiengine applicant.
Although this is a recommended procedure, the urgent warning was aimed at flight instructors who were using this procedure at altitudes too low for continued safe flight.
The NTSB observed that use of such procedures at traffic pattern altitudes may not permit instructors enough time to overcome possible errors on the part of the applicant. The recommendation by the NTSB means that all simulated engine-out operation at the lower altitudes should be accomplished by carefully retarding the throttle and this should be done slowly and carefully to avoid engine damage or failure. This careful technique will protect the engine and at the same time provide for instant power if it is needed.
I am sure an aviation lawyer would make good use of this statement if needed in a civil case against an instructor involved in an accident such as both Camden accidents referred to in the initial post.