2009年10月16日釋字第665號解釋，就刑事訴訟法第101條第1項第3款重罪羈押之規定，以附「相當理由」此一條件作出合憲限縮解釋。對此，雖文獻上已有不少的批評聲音，然自該號解釋作成至今，將近4年，國內仍尚未見此等重罪羈押「相當理由」概念於司法實務發展及所生影響之相關研究。本文即以大法官釋字第665號解釋及其後之相關最高法院裁判為觀察重點，欲藉此觀察在該號解釋作成後，該號解釋中重罪羈押「相當理由」概念之論述對司法實務之運作，是否以及將產生如何之變化及影響。
本文分析相關實務裁判可知，我國實務上，自大法官釋字第665號解釋作成後至今，最高法院本身就重罪羈押「相當理由」概念，不僅對於重罪羈押的決定未生任何重大的實質改變，且所出現的各個問題也都一再映證了解釋作成之初相關文獻所提出的疑義及缺失。本文認為，根本解決之道乃在於立法論上，修法重新檢討重罪羈押之存廢；而在未修法之前，若欲以該號解釋中之重罪羈押「相當理由」作為其判斷標準的前提，最高法院在類似爭議中應透過司法實務運作案例的類型化，乃至於裁判的累積，再輔以學理上的說明，予以補強，如此方有可能增強其說服力。

The criminal felony detention has always been an important legal issue. Besides the constitutional interpretation made by J.Y. Interpretation No. 665, the judicial practice of the criminal felony detention still needs further study. First, this article observes the concept "probable cause" from J.Y. Interpretation No. 665, and discusses J.Y. Interpretation No. 665, including the background issue of J.Y. Interpretation No. 665, intentions, and arguments for interpretation methods. Then, this paper further observes the attitude and demonstration toward the concept "probable cause" of the criminal felony detention in judgments made after J.Y. Interpretation No. 665 and tries to analyze and clarify the stand, change, and development of judicial practice, especially in practical cases made by Taiwan Supreme Court (TSC), in this part, we will figure whether the viewpoints of TSC have been changed or not owing to the interpretation. And we can find that even in the same period, the different opinions from separate courts in TSC are often against each other. Therefore, this article tries to explain and review the concept "probable cause" of the criminal felony detention through the demonstration of the observations on the above-mentioned judgments, and make some criticisms and suggestions.