I suspect that one of the activities a lawyer does in this case is prepping you to answer these questions. Rather than "dunno" the answer could be "It was an unremarkable night, I ate dinner at home, watched netflix, and went to bed". Odds are the browser history/location history on your phone would provide corroboration for the above if needed.
Along that, you would do your own investigation. Look over texts, emails, calls, credit card charges, and use discovery from the other side like location data, surveillance footage, and etc.
This is ALSO why you don’t ever talk to police. You talk to lawyers. If a cop were to ask you the same “where were you at” question, it’s probably better to not answer at all.
