It is an exception to the 'hearsay' Rule of Evidence. Normally, unless it is part of what is cutely called 'res gestae,' in all cases, what a victim of alleged rape says to a third person (not being part of a complaint to Police) following the event is inadmissible. So, say, a fortnight after an alleged rape, a female says to her friend, 'Bill raped me.' That might not be admissible in a Trial because the allegation was not made at the first opportunity, assuming she had opportunities open to her in that fortnight. However, if a complainant says to a friend within minutes (okay, there is elasticity there) and hysterically, 'Bill raped me,' it is admissible under the 'recent complaint' exception. Of course, that leaves open for the defence to validly question a complainant why they did not, for example, complain to Mum when they got home on the night of an alleged rape ~ why she did not tell Mum she had been raped. My point here is that this evidence of whay he said to his Dad is clearly (and obviously) admissible, and he says what would be expected of him. If he rang Dad and discussed how great it was to get a pizza at that time of night and not mention the incident, the Prosecutor would have a field day. But, fact is, he did tell Dad what happened. Clear as mud?