Wielding the cricket bat in his hands, police colonel Johannes Vermeulen knelt down before swinging it at the wooden door in a court reconstruction to show the angle of the marks and to suggest they could only have been made by someone much shorter than him.
The 27-year-old double amputee is charged with the murder of model Reeva Steenkamp whom he shot through the locked door on Valentine's Day last year.
Prosecutors want to prove it was premeditated killing but Pistorius says he was defending himself from what he thought was an intruder.
Pistorius previously stated he had put on his prostheses before smashing down the door but Mr Vermeulen disagreed.
The witness said: "The marks on the door are actually consistent with him not having his legs on and I suspect they must be similar to the height that he was when he fired the shots."
Defence advocate Barry Roux suggested even with his legs on, Pistorius would not be swinging a bat at the same height as an able-bodied person.
The trial continues.