The dead body of Mr. Chastain is found at the bottom of a multistory building. Seeing the position of the body, it is evident that the person jumped from one of the floors, committing suicide.
Mr. Finlay, is a homicide detective who is called to look after the case. He goes to the first floor and walks in the room facing the direction in which the body was found.
Mr. Finlay opens the window in that direction and flips a coin towards the floor. Then he goes to the second floor and repeats the process. He keeps on doing this until he reaches the last floor. Then, when he climbs down he tells the team that it is a murder not suicide.
How did Mr. Finlay come to know that it was a murder?