After WWII, in response to the atrocities of totalitarian states, constitutional rights came to the fore as defense rights directed against the state (i.e. rights of negative status). Constitutional rights in this conception raise legal constraints on the functioning of state power in order to extend as far as possible an individual's field of freedom unhindered by the state power. Constitutional rights protect individual areas of individual liberty against unjustified interventions by state authorities by imposing on the state the obligation to justify any interference while respecting strict procedural and substantive guarantees. If the state has no legitimacy, it must refrain from the intervention. Despite this temporary dominance of the concept of constitutional rights as defense rights, it was impossible to overlook the fact that there are other social forces in addition to the state, which act towards the individual with actual power. If constitutional rights are to guarantee the effective protection of individual areas of freedom, then it is also necessary to establish the responsibility of the state to ensure their enforcement in relation to non-state, private-law forces and entities. In such situation the state no longer acts as an opponent of constitutional rights, which is why its power must be inhibited; the state acts as a guardian of constitutional rights, which is why its power should be encouraged. In other words, the state has not only negative but also positive obligations deriving from the constitutional rights.
In both the German legal framework and the ECtHR case law, the concept of positive obligations is derived on the basis of an objective legal conception of human rights. According to this conception, the human rights are not limited by their defense function, but are considered as the value orientations or building blocks of the (European) constitutional order. The character of convention rights, as an expression of the objective order of values, requires us to apply and interpret them in such a way as to ensure their widest and most effective exercise in all-inclusive tendencies (including in the context of private law relationships).
In assessing a breach of a positive obligation in the context of the right to life, it is first necessary to ask whether a positive obligation arose in the specific case. In German theory, the crucial criterion is whether a specific level of danger to life exceeds a legally permissible threshold. This threshold is concretized by the criteria developed by police law. In police law, a legally relevant danger is defined as a situation which, after an unhindered course of events, is sufficiently likely to cause injury. The danger is such a recognizable, objective, immediate possibility of harm. Unlike in German theory, in ECtHR case law, the key criterion for assessing the emergence of a positive obligation is the question of whether the state knew or should have known about the existence of a risk. In this respect, the assessment criteria in the German case-law are stricter, because they merely focus on a question of whether an objectively unlawful danger has arisen, and not whether the state had known or should have known of such danger.
Once we conclude that a positive obligation of the state exists in a particular case, the legal consequence is a state's obligation to take steps to fulfill the positive obligation. German Federal Constitutional Court (ger. Bundesverfassungsgericht or BVerfG) and ECtHR apply different standards for assessing the fulfillment of positive obligations. BVerfG takes into account a broad discretion of the legislator and defines the standard of assessment of compliance with a protection obligation only where the state authority has not taken protective measures at all or when the measures taken are manifestly inadequate or completely insufficient to protect the objective. In the recent BVerfG judicature in cases involving »legal interests of paramount importance«, this test is replaced by the Untermaßverbots test. Unlike BVerfG, the ECtHR is not so restrained in its assessment of the fulfillment of positive obligations, and in particular the assessment of the fulfillment of operative obligations to protect life, and carries out a more in-depth substantive assessment. In principle, the criterion of reasonableness and proportionality are used as a starting point. The reasonableness criterion means that a positive obligation must be interpreted in a way which it does not impose an impossible or disproportionate burden on the state. The proportionality criterion means that measures taken by a national authority to protect a certain right must be sufficient to effectively protect that right without unduly interfering with conflicting rights.