What does a subjective case pronoun follow?

A subjective case pronoun may not follow anything. A subjective case pronoun can start a sentence or fall somewhere within a sentence.

Examples:

• George takes the train to work. He gets off at 19th Street. (the subjective pronoun 'he' starts the second sentence as the subject of that sentence)
• The train that he takes to work stops at 19th Street. (the subjective pronoun 'he' is the subject of the relative clause)