Administrative Litigation Act Article 152

A witness may refuse to sign a written oath on matters with direct interests with him/her or with the persons provided in Article 145.
中文原文 行政訴訟法第152條
證人就與自己或第一百四十五條所列之人有直接利害關係之事項受訊問者,得拒絕具結。

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