He hobbles all the way out to the observation platform. Very unlikely with his leg in a cast, unless he has a very strong reason.
8 seconds sound clip from the Double Indemnity movie soundboard.
You can hear this line at 01:05:38 in the DVD version of the movie.
Quote context
[...]
- He was perfectly all right and I don't know of any financial worries.
- Let us examine this so-called accident.
- Do what?
- Next, he goes on this trip entirely alone. He has to be alone.
- Once there, he finds he is not alone. There is a man there.
- His name was Jackson. Probably still is.
- He jumps. Suicide. In which case, the company is not liable. You know that, of course.
[...]