Normally the Dekra/TÜV/BMW-Dealer should be able to see weather there was an accident or not. They know how an engine looks like after f.e. 50.000 km. And they are able to see if the paint has been restored or even if its painted a second time. They measure the paint an can tell you if its the originally paint or not.
To be sure that you have the possibility to check the car with Dekra/TÜV/BMW-Dealer give them a call and ask for a date on which you can come with the car.
I think its the best way to buy a car with a highness of safety!
Good luck!