measure would be considered, by a reasonable person examining the objective circumstances, to be involved in a potential violation of a legal interest. A mere possibility based primarily on the intuition of the security authorities that further intelligence
might be obtained is not sufficient for carrying out such measures (see BVerfGE
107, 299 <321 et seq.>; 110, 33 <56>; 113, 348 <377 and 378, 380 and 381>; 120,
274 <328>; 125, 260 <330>). The Constitution thus sets clear limits to lowering the
threshold for crime prevention measures that are carried out covertly and can seriously interfere with privacy; in contrast, with regard to measures involving less serious interferences with privacy, the constitutionally permitted leeway in crime prevention matters is broader.
With regard to the detailed design of the individual powers, what matters substantially for their appropriateness as well as the required specificity is that they be tailored to the weight of each codified interference. The more seriously the surveillance
measures interfere with privacy and thwart legitimate expectations of confidentiality,
the stricter the requirements must be. The surveillance of private homes and the access to information technology systems constitute particularly serious interferences
with privacy.
105
a) Covert surveillance measures must be limited to the protection or legal reinforcement of sufficiently weighty legal interests.
106
For measures that serve a law enforcement purpose and are thus repressive in nature, the weight of the criminal offences in question is relevant for their classification,
which the legislature has divided into significant, serious and particularly serious–
criminal offences, each defined in greater detail. Thus, the surveillance of private
homes requires the suspicion of a particularly serious criminal offence (cf. BVerfGE
109, 279 <343 et seq.>); telecommunications surveillance or the use of telecommunications traffic data collected as a precaution requires the suspicion of a serious criminal offence (cf. BVerfGE 125, 260 <328 and 329>; 129, 208 <243>); while the collection of telecommunications traffic data with cause or observation by means of a GPS
tracker, for example, requires a significant criminal offence – and, in the former case,
one that is specified in the law – (cf. BVerfGE 107, 299 <321 and 322>; 112, 304
<315 and 316>; with regard to the latter decision, see also European Court of Human
Rights (ECtHR), Uzun v. Germany, judgment of 2 September 2010, no. 35623/05,
para. 70, Neue Juristische Wochenschrift – NJW 2011, p. 1333 <1336>, on Art. 8 of
the European Convention on Human Rights – ECHR).
107
With regard to measures that serve to protect against threats and are thus of a preventive nature, what matters is the weight of the legal interests being protected (cf.
BVerfGE 125, 260 <329>). Covert surveillance measures that constitute a serious interference with privacy are only permissible with regard to particularly weighty legal
interests. These include life, limb and the freedom of persons as well as the existence
or security of the Federation or a Land (cf. BVerfGE 120, 274 <328>; 125, 260 <330>)
In contrast, the Federal Constitutional Court has not deemed the unlimited protection
108
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