The context is that A, B, and C just got home. They are now wandering around a big house looking for a group of kids. The 3 are wondering if the kids have been studying. A has not yet talked with C:
[line 1]「本当ですか?勉強していますか?」A-さんはたずねた。「証拠は?」
[line 2] 「C-さんが見ました」B-さんはいった。「勉強しているとかれがいうな���、それが立派な証拠だと思いますが」
Part of line #2 reads:
...勉強しているとかれがいうなら...
Because "かれ" is obviously C, do you really have to say "かれ"?
If you do not say "かれ", how does it change the nuance?