I am not a lawyer, and I don't play one on television.... (An attempt at humor.) To your question, I think there is a principle of being able to challenge an accuser or interview a witness. Otherwise, like the secret police of the Soviet Union, accusations could be made, people arrested, and no one could cross-examine the witness or accuser to test the validity of the claims of the accuser or witness. Being able to confront an accuser in court is essential to minimize misuse of the process. Mistakes still happen, but it is a better system than having secret accusers.