不自證己罪之特權顯諸於被告則爲緘默權，顯諸於證人則爲拒絕證言權，證人恐因陳述致自己受刑事追訴或處罰者，得拒絕證言。證人與被告同有不自證己罪之特權，但因爲二者在刑事訴訟中之身份與角色不同，所表彰之權利內容也因此有所歧異，本文之目的即在釐清此種歧異，並闡明其理論基礎。再者，我國九十二年二月六日公布的新修正刑事訴訟法，修改第一百八十六條、增訂第二百八十七條之二，致證人不自證己罪的實際操作產生顯著的變化：一、舊法第一百八十六條第三款規定，與本案有共犯或湮滅證據關係者，不得令其具結。新法刪除該款規定，依第一百八十一條規定其雖得拒絕證言，如不拒絕證言而爲虛偽之陳述，則構成偽證罪。二、新法增訂第一百八十六條第二項：「證人有第一百八十一條之情形者，應告以得拒絕證言」。舊法對於證人不自證己罪之拒絕證言權，法院或檢察官並無告知之義務，但新法則有。所衍生之問題則爲，如法院或檢察官未踐行該項告知義務，法律效果爲何？三、新法增訂第二百八十七條之二：「法院就被告本人之案件調查共同被告時，該共同被告準用有關人證之規定。」所生問題爲當法院依上法條調查共同被告時，既然準用人證之規定，共同被告所應享有之權利，係屬於被告之緘默權，或屬於證人之拒絕證言權？ 證人非刑事訴追之對象，應不得概括行使拒絕證言權、亦不得只陳述事實之一部。證人之陳述，是否會造成其受刑事追訴或處罰，本文主張若自證人之陳述中，得直接或問接推演出對其不利之證據，證人即得主張拒絕證言權。證人不自證己罪之拒絕證言權、新法對法官或檢察官所課之告知義務，其目的皆在保護「證人」，非爲保護訴訟「當事人」而設。因比，違反此項告知義務所衍生之證人證詞，對訴訟「當事人」仍具證據能力，至於證據之證明力，則由法院個案判斷之。但違反告知義務之證人證詞，在將來對該「證人」追訴或處罰的審判中，基於不自證己罪法理，不得爲證據。 共同被告在本案被告之審判中，其身分及權利義務爲何？在分離審判前，共同被告仍爲被告身分，所行使者爲緘默權，檢察官也不得以共同被告爲舉證方法：在分離審判後，就被告本人之案件調查共同被告時，該共同被告具證人適格，雖然其得拒絕證言，但如不拒絕而陳述，即必須具結及據實陳述，如陳述不賞並應受偽證處罰。惟本文主張共同被告在具結後，如只陳述一部事實而拒絕陳述其他相關事實，應將其已陳述之部分排除，但不應對其處以罰鍰。 偵查中對於「證人」或「被告」的屬性，有時會出現錯亂的情形，今日之證人，有可能成爲明日起訴書所指之被告。在偵查中，如檢察官以「證人」身分傳喚某甲訊問，但之後將甲改列爲「被告」而提起公訴，甲在偵查中以「證人」身分所作陳述。是否得爲證據？本文認爲此一問題，得同時自不自證己罪理論、正當程序理論分析。前者的重點在於人民是否被強迫成爲對自己不利的證人，後者的重心則在於政府機關行爲是否合理、正當，是否侵犯法之正義感。若以不自證己罪理論分析，本文主張若檢察官未告知甲有拒絕證言權，甲等於被強迫成爲證人，甲在偵查中之陳述不得成爲審判中之證據；但如檢察官已告知甲得拒絕證言，甲有選擇不陳述的權利，其在偵查中之陳述則具證據能力。若依正當程序分析，如檢察官係「蓄意」規避第九十五條所定之告知義務，不論其是否踐行第一百八十六條第二項之告知義務，該陳述皆無證據能力。如檢察官「非蓄意」規避第九十五條所定之告知義務，殊難否定該陳述之證據能力。

This paper examines the witness' privilege against self-incrimination under Taiwan's new Code of Criminal Procedure. Before September 1, 2004, Article 186 of Taiwan's Code of Criminal Procedure provided that cooffenders are not allowed to make sworn testimony at trial or prosecutorial investigation proceeding. This was a very bizarre provision, of course. At then, neither parties nor the court could require co-offenders to make statements under oath. In other words, co-offender's unswom statements could be admitted into evidence at trial, no matter they are favorable or unfavorable to the defendant. A co-defendant was never liable for perjury even if they lied before the court since they were not allowed to take oath. After September 1, 2004, the new Article 186 of Taiwan's Code of Criminal Procedure requires that all witnesses, except those who are under age 16 or could not understand the meaning of oath, have to take oath in making statements at trial or prosecutorial investigation proceedings. The new provision has changed the trial practice dramatically. On the one hand, a co-offender's statement is not admissible at trial unless he is under oath. On the other, a co-offender does not enjoy the privilege to lie at court anymore. At the same time, Section 2, Article 186 of the new Code of Criminal Procedure provides that a judge or prosecutor shall warn the witness of his privilege against self-incrimination before he testifies. This is also a new provision added into the new Code. Before September 1, 2004, a judge or prosecutor did not have such a duty to warn the witness of his privilege against self-incrimination since co-offenders were never allowed to take oath and would never commit perjury. Section 2, Article 186 was added to warn witnesses to think carefully before testifying because they are not immune from perjury anymore. Before September 1, 2004, it was not important to define the meaning or the scope of the witness' privilege against self-incrimination since they were free to lie under the law. However, it becomes an extremely important issue because they are allowed and, sometimes, forced to take oath and make statements at trial. It is important to know when and on what conditions a witness could or could not assert his privilege against self-incrimination under the new Code.