Detective's Logic in Murder Mystery

What is the case?

Obviously, the person can't jump with window closed or come outside of the window & close that window from inside.

The detective checks if windows is closed from inside by opening window & flipping the coin toward the floor. He flips the coin to mark the count of that particular floor where window was closed from inside & he has to open it to flip the coin.

At the end, he collects as many coin as floors of that building. So he concludes that no floor had open window from where the person might have jumped.

 
So, he concludes that it was the murder and not the suicide.