Part two: non-party discovery

Non-party discovery, is when the lawyer sent the letter directly to your parents to request production of such evidence.

Again, according to FRCP, the lawyer has the subpoena power to do so. Typically non-party can object such request by written notice on basis of privilege. For other grounds, the non-party must file a timely motion to the court issuing the subpoena to challenge such request, either on basis of undue burden/cost which outweighs relevance, or that the information is not under the non-party's control.