be the case that
fixed phr.. B1 Intermediate Oxford
fixed phr.. to be true or to be the actual situation.
fixed phr.. to be the factual state of affairs; often used as a dummy subject construction to introduce a clause describing a reality.
It might be the case that he forgot.
If it is the case that the flight is cancelled, we will need a hotel.
While many assume the economy is recovering, it may not be the case that every sector is seeing growth.
Usage
usually follows the dummy subject 'it' and is followed by a 'that' clause.
Teaching tip
this phrase is a more formal or wordy way of saying 'to be true'; it is very common in academic writing and logical arguments.
Pitfall
It is the case of he is late.It is the case that he is late.use a 'that' clause to follow the phrase rather than a prepositional phrase with 'of'.