in·ter·vene /ˌin-tər-'vēn/ vi -ven·ed, -ven·ing
1: to occur, fall, or come between points of time or events
may be held liable even though other independent agencies intervene between his negligence and the ultimate result — Hooks Superx Inc. v. McLaughlin, 642 N.E.2d 514 (1994)
2 a: to come in or between by way of hindrance or modification
intervene to stop a fight
b: to become a party to a legal proceeding begun by others in order to protect an alleged interest in the subject matter of the proceeding
the Commissioner of Internal Revenue was granted leave to intervene — P. A. Freund compare implead, interplead, join
in·ter·ve·nor /-'vē-nər, -ˌnȯr/ n
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.