Cracked window inspection

Our apartment window cracked without being touched. Our landlord is trying to make us pay for damages and has a window expert saying that the crack must be due to us hitting the window and no other option is possible, even though I did not hit the window and saw it crack whilst I was watching TV. I suspect thermal cracking as there is a radiator under the window that was turned on the same day for the first time since last winter Apparently, I need an expert to come and inspect the window and provide a statement that it could have been cracked due to fault, temperature change, something else. The window is double glazed. Cracked on the inside. In short, we did not break the window, and we need to prove that somehow! Apartment located in haugerudveien