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.
Trial of Impeachment. The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.