Final answer:
The records of the Probate Court should be searched to identify parties with an interest in the estate of a deceased individual, as these courts specifically deal with matters of wills and estates.
Step-by-step explanation:
To find the names of the parties who have an interest in the estate of a deceased individual, an investigator should search the records of the Probate Court. Probate courts are specialized courts in each county that handle matters pertaining to wills and estates, including the distribution of assets of the deceased. Parties with an interest in the estate, such as heirs, beneficiaries, and creditors, can usually be found in the probate filings and proceedings.
For comparison, the County Civil Court typically handles civil cases involving claims that are not related to deceased individuals' estates, while the U.S. District Court is a federal court that deals with federal matters rather than probate issues. Therefore, the correct answer to the question is c. Probate Court.