An indexing system for case law in which you can search based on topic is called a?

The correct answer is "Digest." A digest is a type of indexing system specifically designed for case law that organizes legal cases by topics. This allows legal professionals, including paralegals, to efficiently locate relevant case law based on specific subject matter. Digests provide summaries and classifications of cases, making it easier to find pertinent decisions without the need to sift through entire case reports.

In contrast, a case law database is generally an electronic or online repository of case law, often including various search functions but not necessarily structured around topics in the same systematic way that a digest is. A citation index typically refers to a system that indexes legal documents based on their citations, helping users track cases and related legal literature rather than organizing by subject matter. A legal encyclopedia offers a broad overview of legal topics but does not specifically provide a case law indexing system.