It is logically impossible to see a man’s face or belt buckle when he is facing away from you.

Unfortunately for him, Captain Hargrave forgets this when he says that he saw Jenkins’ gold tooth and belt buckle as he watched him climb up the stairs.

And we know there was no point at which Jenkins was at an angle that faces Hargrave because he himself said that it’s a good thing Jenkins didn’t turn around and see him.

This reveals that he is lying, making Captain Hargrave the murderer!