Nexus test refers to a pursuit undertaken by a private person in concert with a governmental entity or state official. It results from a private person performing public functions and thereby being subject to claims under the civil rights laws. It is also known as joint activity. The nexus test for determining whether a person is armed requires that there must be a relationship between the defendant, the crime, and the deadly weapon in order to establish that the defendant was armed for purposes of the deadly weapon enhancement statute.
Under the direct nexus test, the inquiry must be whether there is a sufficiently close nexus between the state and the challenged action of the regulated entity so that the action of the latter may be fairly treated as that of the state itself. Nexus test is also known as symbiotic-relationship test.[Wabash Pub. Co. v. Arlington Int'l Racecourse, Inc., 1992 U.S. Dist. LEXIS 7073 (N.D. Ill. May 26, 1992)].