Constitutional Court Procedure Act Article 69

(Dismissing a Petition for Impeachment)The proceedings of the cases under this Chapter shall not be affected by the expiration of the term of office of the impeached, by the dissolution of the Legislative Yuan, or by the ending of the term of the Legislative Yuan. Notwithstanding, if the impeached resigns from office, no longer holds the post, or dies prior to the pronouncement of the judgment, the Constitutional Court shall dismiss the petition by an order.
中文原文 憲法訴訟法第69條
本章案件程序之進行,不因被彈劾人卸任、立法院之解散或該屆立法委員任期屆滿而受影響。
但被彈劾人於判決宣示前辭職、去職或死亡者,憲法法庭應裁定不受理。

English translation for reference only; the Chinese text prevails. Not legal advice.