How would you define the function and responsibilities of technical leader?

There are numerous disciplines in the area of applied science and technology. These areas contain endless opportunities for technical leadership.

However, as a technical leader there comes a high degree of responsibility with a specific skill set and knowledge in a particular area. How would

you define the function and responsibilities of technical leader? What KSAs (Knowledge, Skills and Abilities) must a technical leader possess as the SME (Subject Matter Expert) in a given discipline to lead a group or organization?