§1. Attentive to what the litigants may bring forward, the judge is to determine in a decree the individual items upon which the services of the expert must focus.
§2. The acts of the case and other documents and aids which the expert can need to fulfill his or her function correctly and faithfully must be turned over to the expert.
§3. After having heard the expert, the judge is to determine the time within which the expert must complete the examination and produce the report.
Source: Code of Canon Law (Vatican.va)