turning point. n. 1. a moment when the course of events is changed: the turning point of his career. 2. a point at which there is a change in direction or motion. 3. (Mathematics) maths a stationary point at which the first derivative of a function changes sign, so that typically its graph does not cross a horizontal tangent.
Because high Crimes and Misdemeanors was a term of art used in English impeachments, a plausible reading supported by many scholars is that the grounds for impeachment can be not only the defined crimes of treason and bribery, but also other criminal or even noncriminal behavior amounting to a serious dereliction of duty.
During the Federal Constitutional Convention, the framers addressed whether even to include impeachment trials in the Constitution, the venue and process for such trials, what crimes should warrant impeachment, and the likelihood of conviction.