Verified answer

Pronouns do not vary accoring to case. I am still me (or I) whether in the past, present or future. The subject of a sentence will either be a noun or a personal pronoun. Look for the active verb and see what it relates to - it will always have a subject (it may be implied), and usually though not always have an object. Look at the subject to see whether it is governed by a noun or a pronoun.

Do you mean ?..... him, her, he, she, it = 3rd case

you (singular or pl) = 2nd case

I, we , us, our = 1st case