bb) Furthermore, it also follows that, when carrying out surveillance measures, the
protection of the core area must be taken into account on two levels. Firstly, at the data collection level, arrangements must be made in order to rule out as far as possible
the unintentional collection of information stemming from the core area. Secondly, at
the level of the subsequent analysis and use of the information, the consequences of
an intrusion into the core area of private life that was not prevented must be strictly
minimised (see BVerfGE 120, 274 <337 et seq..>; 129, 208 <245 and 246>).
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d) In this context, the legislature must design the protection of the core area of private life differently for each surveillance measure, depending on the type of power
and its proximity to the absolutely protected area of private life (cf. BVerfGE 120, 274
<337>; 129, 208 <245>). In doing so, it must, however, make legislative arrangements on both levels.
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At the data collection level, with regard to measures likely to result in interference, a
pre-emptive examination must ensure that situations or conversations relevant to the
core area are excluded to the extent that this can be done in advance, practicably and
with a reasonable amount of effort (cf. BVerfGE 109, 279 <318, 320, 324>; 113, 348
<391 and 392>; 120, 274 <338>). Under certain circumstances, with regard to conversations with persons enjoying the highest level of personal trust, which are typically indicative of confidential situations, the presumption may be warranted that these
belong to the core area and may not be subject to surveillance (cf. BVerfGE 109, 279
<321 et seq.>; 129, 208 <247>). The legislature may design this presumption to be
refutable and in particular make it dependent on whether there are indications in an
individual case that criminal acts will be discussed. In contrast, the fact that apart from
highly personal issues, everyday matters will also be discussed is not sufficient to refute the highly confidential nature of a conversation (cf. BVerfGE 109, 279 <330 >). In
any case, the measure must be discontinued when it becomes apparent that the surveillance is intruding upon the core area of private life (cf. BVerfGE 109, 279 <318,
324, 331>; 113, 348 <392>; 120, 274 <338>).
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At the level of analysis and use of data, the legislature must provide for cases in
which it was not possible to avoid collecting information relevant to the core area, by
requiring, as a rule, the screening of the collected data by an independent body that
filters out the information relevant to the core area prior to use by the security authorities (cf. BVerfGE 109, 279 <331 et seq.>; 120, 274 <338 and 339>). However, the
constitutionally required procedural safeguards do not, in every type of case, require
the creation of independent bodies other than the investigative bodies of the state (cf.
BVerfGE 129, 208 <250>). The necessity of such a screening depends on the type,
as well as, if applicable, the design of the power in question. The more reliably the
collection of information relevant to the core area is already avoided at the first level,
the more likely a screening by an independent body can be dispensed with, and vice
versa. This does not affect the fact that the legislature has the possibility to enact the
necessary provisions to provide the investigative bodies of the state with short-term
possibilities for action in exceptional cases in case of immediate danger. In any case,
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