where applicable. It will normally not be sufficient for the additional ordering of visual
surveillance to cite merely the increased ease at matching voices; rather, more significant grounds relevant to the success of the surveillance are needed. In the context
of applying the law, these requirements can and must be taken into consideration.
§ 20h sec. 1 nos. 1 and 2 BKAG, which lays down audio and visual surveillance of
private homes as separate surveillance measures which must therefore be examined
separately, provides a sufficient basis for this.
c) The definition of the persons potentially addressed by the surveillance measures,
however, is partially disproportionate and incompatible with the Constitution.
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aa) There is nothing to object to with regard to § 20h sec. 1 no. 1 a BKAG, which
provides for the authorisation to order the surveillance of private homes targeting persons responsible within the meaning of §§ 17, 18 BPolG (see above C IV 1 c).
187
There is also no cause for objection in that § 20g sec. 2 BKAG thereby permits the
surveillance of such persons not only in their own home but also in the home of third
parties, if the target persons are present and measures in the home of the target person alone would not lead to protection against the danger. However, the Federal
Constitutional Court has formulated restrictive standards of interpretation with regard
to such surveillance measures in the homes of third parties […] (cf. BVerfGE 109, 279
<356 and 357>).
188
bb) § 20h sec. 1 no. 1 b BKAG, which permits the surveillance of private homes with
respect to persons whose involvement in specific preparations justify the assumption
of the commission of terrorist offences, is constitutionally sound.
189
Unlike § 20g sec. 1 no. 2 BKAG, the provision does not create separate grounds for
interference applying particularly far ahead of the time of the danger. Instead, it requires – in accordance with Art. 13 sec. 4 GG – imminent danger to qualified legal interests for whose protection the surveillance must be necessary. Moreover, the class
of persons addressed by these measures is sufficiently limited: By requiring knowledge of specific preparations of – more narrowly qualified – terrorist offences, the provision stipulates the existence of an occurrence that is specific with regard to its type
and temporally foreseeable. In doing so, it provides a basis for carrying out such measures that satisfies the constitutional requirements (see above, C IV 1 b).
190
cc) The authorisation of the surveillance of private homes with regard to contacts or
accompanying persons (§ 20h sec. 1 no. 1 c BKAG), however, is incompatible with
Art. 13 secs. 1 and 4 GG. It is disproportionate.
191
The surveillance of private homes is a particularly serious interference with privacy.
By its nature, it has a more serious impact than surveillance measures outside of private homes or than telecommunications surveillance. The weight of its interference is
paralleled only by interferences with information technology systems. For this reason,
the appropriateness of such a measure can only be ensured if it is restricted from the
outset to exclusively capturing conversations of the target person responsible for the
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