Interesting (I did not know that- I read the article). Now, what if the witness refuses to make the aknowlegement? Or can the witness simply refuse to take the stand altogether?

This scenerio seems far fectched- But could be used if, for instance, a man commited murder and his friend was the sole and/or key witness. The man could face death if convicted so the friend faces lessor charges to protect his friend. What would the charges be, and could he avoid them?