Normally only as subject. Often it has the same extra semantic force as does hwyw, i.e. "he himself, he is the one who" and this was clearly understood in the LJLA tradition where it is found only as a subject.
The etymology has long been debated, but we are convinced that it is of the same basic type as the repeated form hwyw with vocalic dissimlation and loss of initial heh. What remains unclear, however, is how many LJLA examples are simply due to scribal change toward the standard JBA usage, as clearly happened in the language of the Zohar. We suggest that any example without a clear emphatic function may well be the result of such a change, for in almost all such cases variant texts have simple הוא.