Before Gen 5.
No because poison disappears at 1 HP so Shedinja would live.
Source:Experience
Outside of battle, Shedinja immediately recovers from Poison after four steps in Generation IV onwards, whereas in Generation III it will immediately faint after four steps.
http://bulbapedia.bulbagarden.net/wiki/Shedinja#1_HP_trivia ____ So in Generation III, Shedinja will faint. In Generation IV, Poison is cured.