Once the expert has "established" this "somewhere else," though, and asserted that BK was there, if BK took the stand (which I'm sure he never will), couldn't the prosecutor ask him what he was doing at xyz "established" point?
yes - so we end up back at my original question. How do you get in an alibi of star gazing if BK does not testify?
IMO he would have to, unless someone else (e.g his parents?) are going to say he had a habit of doing this?