I’m a death investigator in NYC. Jumping from a tall building is actually very common here.
There are many things we do during a death investigations that gives us a good idea of whether a descent was a suicide or not.
First, we check for history of suicidal attempts or ideation. We speak ‘to friends and family to get a sense of what was going on in a person’s life. Also, we look for notes.
Most often, people jump from a window in their apartment or from the roof. If someone jumps from a roof, many times, there are cameras that overlook the roof or the hallway outside of the door leading to the roof. So we can see who was going up there.
Also, we take measurements of the area the person descended from. Some walls are very high, and it would be very unlikely that another person would have had the ability to push or throw them, or they jumped from an place difficult to access , or too dangerous for someone who wasn’t the one planning on dying.
If in an apartment, simple things like the engagement of locks and latches. We also measure the window to piece together what we think may have happened, and look for things like chairs or ladders near the window that someone may have used to get out of the window.