"Can't have been".

Just heard it awhile ago on the internet. I've come across such phrase before, have you?

It is uncommon but possible in the proper context. Are you sure is wasn't " Someone could / couldn't have been....?" This construction is usually used for hyphetical or counter-facutal situations.

In the UK, "can't have been" is reasonably common, both colloquially as a sentence by itself (e.g. expressing disbelief that something happened as described), and in general sentence contexts such as "It can't have been easy", "We can't have been trying hard enough", and so forth.

Whether or not it is the " Across the pond " syndrome, I supposed the core meaning is understood relatively speaking. But from a linguistic persepctive, " Can't " may be border-line considered improper in AmE when used in a disbelief or counter-factual context, in my opinion.

Scenario: Police came to your house. Your teenager son was accused of being involved in an hit-and-run accident l