Legal Research Explained: Process, Types & Best Practices

Legal research is the bedrock of any sound legal argument, a systematic process of identifying, verifying, and synthesizing legal authority to answer specific questions with a defensible, citable basis. Unlike general research, its defining discipline is the strict hierarchy of authority: primary sources always outweigh secondary ones, and every conclusion must trace back to independently verifiable sources.

This definitive guide from OASIS Research & Writing clarifies what legal research actually involves, step by step—from understanding the hierarchy of authority and different types of research to navigating common pitfalls and leveraging AI responsibly. It's the difference between an argument that holds up under scrutiny and one that quietly falls apart.

Download the original PDF (22 Legal-Research-Explained-OASIS.pdf)

What Legal Research Is

Legal research is the systematic process of locating, evaluating, and synthesizing legal authority to answer a specific legal question. It differs from general research primarily in its authority structure: legal conclusions are only as strong as the primary sources they cite, and legal readers will test every citation.

The Hierarchy of Legal Authority

Every legal argument rests on a chain of authority. The weight given to different types of sources is critical:

The rule that matters most: a conclusion resting only on secondary commentary, however well-written, is not yet a legal conclusion — it is a starting point for finding the primary authority that actually governs.

Authority Type	Examples	Weight
Primary — binding	Constitutions, statutes, regulations, binding precedent from a higher or equal court in the same jurisdiction	Highest — controls the outcome where directly on point
Primary — persuasive	Precedent from other jurisdictions, lower-court decisions, obiter dicta	Persuasive only — can support an argument, cannot control it
Secondary sources	Legal textbooks, law review articles, practitioner commentary, legal encyclopedias	Explanatory — helps interpret primary authority, never substitutes for it

Types of Legal Research

• Case law research: Tracing how courts have interpreted a legal question, and whether a precedent is still good law.
• Statutory interpretation: Determining what a specific legislative provision requires, using the text, legislative history, and judicial interpretation.
• Regulatory research: Identifying applicable regulations and agency guidance, which change more frequently than statutes.
• Comparative/jurisdictional research: Assessing how a question is treated across multiple jurisdictions.
• Due diligence legal research: Verifying a counterparty's legal standing, litigation history, or regulatory compliance before a transaction.

The Legal Research Process, Step by Step

1. Frame the legal question precisely. A vague question produces an unusable answer; a precise one produces a usable one.
2. Identify the governing jurisdiction. The same question can have different answers across jurisdictions.
3. Locate primary authority first. Before consulting secondary commentary.
4. Verify the primary authority is still current. Check for amendments, repeals, or later cases that have overruled or distinguished it.
5. Apply the authority to the specific facts. Distinguishing the client's facts from the precedent's facts where they diverge.
6. Document contrary or unsettled authority explicitly. Rather than presenting the answer as more settled than it is.
7. Have the analysis independently reviewed. Citation and currency errors are easy to miss in one's own work.

Sources and Tools Professionals Actually Use

Professional legal researchers work from official government legislative portals, court judgment databases, and licensed legal research platforms that track amendments and citing references — not general web search, which cannot reliably confirm whether a case is still good law.

Legal Citation: Why Precision Matters

Legal citation isn't a formatting preference — it's how a reader locates and verifies the exact authority relied on. An imprecise citation can send a reader to the wrong passage or case entirely, undermining the credibility of the entire document.

AI in Legal Research: Uses and Limits

AI tools can accelerate the search phase of legal research. However, they cannot yet reliably confirm whether a case is still good law, and AI-generated legal citations have a well-documented history of being entirely fabricated. Every AI-surfaced citation must be independently verified against the primary source before it appears in a legal document.

Common Mistakes in Legal Research

• Relying on a case without checking whether it has been overruled, distinguished, or superseded.
• Citing secondary commentary as though it were binding authority.
• Applying precedent from the wrong jurisdiction without noting it is persuasive, not binding.
• Accepting an AI-generated citation without independently locating and reading the actual source.
• Omitting contrary authority rather than distinguishing or addressing it.

Best Practices

• Always confirm a case is still good law before relying on it.
• Distinguish binding from persuasive authority explicitly in the analysis.
• Verify every AI-assisted citation against the original primary source.
• State the jurisdiction and scope of the question at the top of the document.
• Have a second, independent reviewer check citations before delivery.

Key Takeaways

• Legal research is built on a strict hierarchy: binding primary authority outranks persuasive authority, which outranks secondary commentary.
• Currency checking — confirming a case is still good law — is not optional.
• AI accelerates search but cannot replace independent verification of every citation.