Hi Tim2tom,
You'd initially be cautioned regarding an offence and taken for formal questioning. Anything you say may be used as evidence against you. Thereafter, if you're arrested then the gardai can detain you for up to 24 hrs for further questioning, which is significant in this context. At the end of this detention they must either charge you or not. They can't re-arrest though and restart a fresh 24 hr holding period unless new material evidence becomes available.
I am unaware whether the alleged victim sought immediate legal representation, which would not be necessary for filing a criminal complaint. It would also contrary to the narrative of a shell shocked victim who has PTSD following a brutal sexual assault. Typically a victim would confide in a friend who would bring them to the gardai and medical professionals discreetly.
Allegedly there are numerous other points of physical evidence which would indicate that the matter was not consensual. This would include physical injuries and allegedly a foreign object which had to be removed from the victim's body by medical professionals. Pretty horrendous stuff, allegedly.
So this person was arrested and held for 24 hrs. If he was charged they let him roam free until trial? Can he leave the country while this process is ongoing? Sorry, I am not familiar with the legal system there.