The detectives saw the balcony with their own eyes. They had no doubt it was where Rebecca went over the railing. The picture clearly shows that, IMO.
Re your comment on the balcony rail...
To the best of my recollection and after checking my notes, during testimony when the lead detective was asked about fingerprints on the balcony rail she said there were no fingerprints taken on the balcony rail.
(The police apparently returned several weeks later to seek additionally evidence, but did not to lift prints from the balcony rail then either, as she explained that the weather would have probably degraded any available prints ( as it was outside)
When asked about the footprints she said no proper analysis was done of the prints. When asked why she said it was because they looked consistent with RZs foot size and also said it was felt unnecessary as there was no indication of a physical struggle
However, the balcony rail was apparently swabbed for DNA, but there was found to be none present when it was tested.
She was then asked about the 11 gap in the thick film of dust on the balcony rail, and was the body checked for any transfer, she said not to her knowledge and referred to the medical examiner.
Also, during the motion experts testimony, a demonstration showed that RZs center of gravity was too low for her to gain enough impetus to fall over the balcony of her own volition, also compounded when combined with her legs being bound.
( There had been a demonstative of the balcony floor and rail set up in the court to show the jury.) The expert had said/ demonstrated it was a scientific / physical impossibility for her to get over with her hands and feet bound.
The defense then argued that RZ could lay her weight on her belly and roll herself forward and over the balcony, when she had gone far enough forward, eventually, she would roll beyond a tipping point, and by kicking her tied legs up behind her she could gain enough impetus to go over the rail.
However, in redirect by Greer, photographic visuals of RZ naked torso were then shown to the court. RZs belly and hip region shows no superficial scraping injury which would be evident if the rolling and scraping motions as were suggested to get over over the rough balcony rail were played out. ( close up images of the balcony rail were shown and they looked quite ragged and uneven in places.) her front belly/torso was also totally clean and showed no dirt or dust of any description.
(It was suggested in the testimony process by Greer that the missing rail dust could have been a result of wiping )
So there was no bodily injury, superficial or otherwise, no dirt transfer, no DNA on the rail, no analysis of the footprints - and the rail was not tested for fingerprints.
I will leave you to draw your own conclusions of the balcony rail evidence.
( paraphrazing from my recollection, my notes and my opinion of what was presented)