A test case is not a test.
A recipe is not cooking. An itinerary is not a trip. A score is not a musical performance, and a file of PowerPoint slides is not a conference talk.
All of the former things are artifacts; explicit representations. The latter things are human performances.
When the former things are used without tacit knowledge and skill, the performance is unlikely to go well. And with tacit knowledge and skill, the artifacts are not central, and may not be necessary at all.
The test case is not the test. The test is what you think and what you do. The test case may have a role, but you, the tester, are at the centre of your testing.
Further reading: http://www.satisfice.com/blog/archives/1346