In the UK's equivalent of America's Miranda Rights, what does the second part of the first sentence mean? [closed]

This is really about law, not English, but easy enough.

In US law, not only is a defendant allowed to remain silent, but the fact that he/she remained silent cannot be used against them at a trial. For example, at the time of trial, if the defendant claims they were with someone when the crime happened, the prosecution is not allowed to say "well why didn't you say that when police asked you where you were?".

In UK law that last part isn't true. The defendant is allowed to remain silent, but at trial the prosecution is allowed to ask why they didn't say where they were when questioned by police.

"It" is the dummy "it" used in phrases like "it is raining".