Questions of British useage

I am writing a story that includes the first born son of an earl:

1. When he goes on a witness stand and gives his name to the judge does he say, "My lord" after as in "Cornel Richard Lystra, my lord?" or does he leave out the "my lord?"

2. Would a sevant talking to him use "sir" or "my lord?"

I'm a Yankee, so don't know much about nobility.

shalimar