近年來，警察基於危害防止之目的，特別是對抗國際恐怖主義之犯罪或危害，於必要時，輒需以秘密方式或運用科技工具對特定對象進行跟蹤監視調查，蒐集各種個資情報與犯罪證據。早期實務見解多認為此等跟蹤監視調查尚非屬強制的警察活動，毋須有法律的特別根據。但跟蹤監視調查活動若係以秘密的、長期的、有計畫的、持續性的蒐集特定對象等個人資料，必要時並輔以科技工具，累積相加的結果，極有可能淪為全面監控之勢，顯已侵害人民的隱私基本權。最近德國聯邦憲法法院針對跟蹤監視調查等措施作成相關判決，認為該等監視調查措施之實施，不僅需要有法律根據，更需要受到合憲性的評價，如比例原則中的正當程序要求，尤其是預防的法官保留原則之約制，似乎亦得作為降低該等職權行使門檻之程序上補償，但如此能否通過合憲性審查，不無疑慮。為研析適正化的跟蹤監視調查法制，本文將從治安維護與人權保障之均衡維護著眼，探討跟蹤監視調查措施之權利侵害性，檢討分析我國現行跟蹤監視調查之法制與實務上問題，評析德國聯邦憲法法院相關裁判例建構之法理，進而研析出符合正當法律程序原理之跟蹤監視調查法制。

In the last two decades, the police, if necessary, may often covertly or with technical means collect personal data in the context of the protection against threats and the prevention of criminal offences (particularly the protection against threats from international terrorism). The issue of covert surveillance has received considerable critical attention and is very controversial with respect to the violation of fundamental rights. However, previous cases decided by the courts of law in Taiwan has mostly been considered to indicate that such covert surveillance measures (particularly the secret surveillance and recording of non-public speech, the recording of images, the use of tracking devices, and the use of police informers and undercover investigators) are not compulsory methods, nor do they require the legal basis for interference. Furthermore, these covert surveillance measures are based on the long-term, organized, and continuous data collection for targeted individuals supplemented by technological devices when necessary, and might also involve covering third parties for inevitable reasons. These measures on the whole can be regarded as an exceptionally serious invasion of privacy when aiming and using modern technology to record as many statements and movements as possible. Recently, the Federal Constitutional Court in Germany ruled on the covert surveillance measures of the Federal Criminal Police Office Act on April 20, 2016. This judgement indicated that these covert surveillance measures need to satisfy not only the legal basis for interference, but also the constitutionality requirements, such as the due process of law in the principle of proportionality. If the standard set by the State for operating covert investigative activities affect particular protected areas of privacy or demonstrate a particularly high intensity of encroachment, the weight of interference with fundamental rights shall be considered by appropriate procedural precautions. Moreover, legal access must normally be subject to a court order and in the form of procedural compensation. However, doubts continue to arise concerning whether this procedural precaution (particularly the reservation of a judicial order) would be sufficient to lower the threshold for crime prevention measures that are carried out in secret with a possible serious invasion of privacy. This paper examines the balances between the interference of secret surveillance measures and the protection of fundamental human rights, and further analyzes the weight of interference and its constitutional limitations on the protection of fundamental human rights. The study then reviews the relevant legal cases from the Federal Constitutional Court in Germany and addresses supervisory issues and investment regulations in Taiwan. Lastly, it provides suggestions and propose reasonable regulations of surveillance and investigation with the principle of due process of law.