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Legal Research and Writing - Spring 2020

Basics of Boolean Logic

Boolean Logic is used heavily in computer science, mathematical sets, and database logic.  They are essentials tools used to either broader, or narrow, your search results.  Utilizing Boolean Logic can increase your search precision and increase relevancy - thereby giving you a far shorter, and more relevant, list of search results.  This can save you time as you have less material to skim through to find sources that answer your research question.

Using OR

The Boolean operator OR is the default in Westlaw, Lexis, and Bloomberg.  If you place a space between terms the operator OR will be assumed.  For example:

Adv: domestic violence


This search query will catch all materials that contain EITHER "domestic" OR "violence".  

Using AND

Use the Boolean operator AND to narrow your results.  It will tell the database that ALL terms must be present in the search results.

For example:

Adv: domestic AND violence AND probation


This search query will only produce search results where ALL of these terms are present.

Using NOT

You may encounter a research problem where you want to exclude materials that discuss a topic using the same terms but address something you are not looking for.  In these scenarios, the Boolean operator NOT is useful.  It is used to exclude a specific term.

For example:

Adv: domestic AND violence AND probation NOT firearm


This search query will only produce results that include "domestic" AND "violence" AND "probation" but will exclude any materials that include the term "firearm".