"Interrogator": "Are you sure both of them were the same person?", 
"Interrogee": "The only resemblance between them was the black boot. Other than that, it was never confirmed that the woman who saw the man dumping the body and the woman who came to the washroom were the same. Another fact is that the woman who came to the washroom knowing that the man had murdered her sister could contribute to the idea that she was the same woman."