When personal pronouns are used as subjects, ordinarily your ear will tell you the correct pronoun. Problems sometimes arise, however, with compound word groups containing a pronoun, so it is not always safe to trust your ear.

His stepfather and he is the subject of the verb had quarreled. If we strip away the words his stepfather and, the correct pronoun becomes clear: he had quarreled (not him had quarreled).

When a pronoun is used as a subject complement (a word following a linking verb), your ear may mislead you, since the incorrect form is frequently heard in casual speech. (See “subject complement,” 47b.)

If kidnapper was he seems too stilted, rewrite the sentence: During the Lindbergh trial, Bruno Hauptmann repeatedly denied that he was the kidnapper.