Unitech - Flat Possession

I am caught up in the Unitech racket and awaiting possession for a flat. Tricky bit is that I was given the possession letter about a year and a half back saying I will get possession in 45 days.

However, because of builder walk-outs and what nots, I still have not received possession because finishing is not completed.

How can I prove that the apartment is not ready for possession and the delays are not on my part?

Thanks!