Thank you very much for the links, Bill. I found the first two earlier today, but the third has a more complete sample Letter of Rights than what I found. The letter has to exist in all EU countries (except Denmark). The tricky part is how much is someone told at the time of their arrest, and how are interrogations conducted in Italy? They have a very complex legal system where prosecutors sometimes conduct interrogations, judges sometimes go out and gather evidence, and cases can take years to work their way through the system. Zzzz.
In my case, I intended to have two detectives lead a team that's hunting for a serial killer who may be the Antichrist. One detective is from the Vatican Gendarmerie, which is too small to have the resources (e.g., a CSI team). The other detective is from the Italian police, which has the resources and cooperates with the Vatican in many police matters in real life. Based on everything I read today, I have no idea whether/when to involve a prosecutor and a judge in the mix. Obviously, the Antichrist isn't going to submit to arrest and interrogation, but there are numerous witnesses and potential suspects that I need to include for story purposes.
Since it's a hunt for the Antichrist, I'm now thinking of using a special ops team who are sworn to secrecy to reduce the odds of word getting out that the End Times have arrived, thereby panicking the world and bringing every reporter from around the globe to Rome. I have the option of allowing that team to operate unlike the Italian/Vatican police when it comes to due process. That seems like my best option.