1. Art. 13(3) of the Constitution, introduced by the Law of 26 March 1998, is not in conflict with Art. 79(3).
2. The inviolability of human dignity under Art. 1(1) of the Constitution entails the absolute protection of the central core of the individual’s private life; it must not be infringed by acoustic surveillance of domestic premises in pursuit of criminal investigations (Art. 13(3)), nor is any trade-off possible between the inviolability of the home (Art. 13(1)), read with Art. 1(1)), and the public interest in the prosecution of crime.
3. Acoustic surveillance of the home does not necessarily infringe the element of human dignity inherent in Art. 13(1) of the Constitution.
5. If acoustic surveillance of a home discloses information appertaining to the central core of an individual’s private life it must be discontinued; all records of it must be excised, and no use may be made of any such information.
6. The provisions of the Code of Criminal Procedure as regards acoustic surveillance of homes in pursuit of criminal investigations do not wholly meet the constitutional requirements of the protection of human dignity (Art. 1(1)), the principle of proportionality in the Rechtsstaat, the guarantee of effective protection of rights (Art. 19(4)) or the right to a fair hearing (Art. 103(1)).
 The constitutional amendment introduced as Art. 13(3) is constitutionally unobjectionable.
 1. Art. 13(3) permits a restriction of the basic right to the inviolability of the home under Art. 13(1). …
 At the time the Constitution was being drafted the primary function of Art. 13(1) was to protect the resident from the unwanted physical presence of state functionaries. Since then, new ways of infringing the basic right have developed, for techonology today makes it possible to invade domestic space without actual physical intrusion. It would frustrate the purpose of the basic right if the guarantee of Art. 13(1) did not reach the surveillance of homes by technical devices deployed outside its curtilage. Accordingly Art 13(3) does constitute a substantive limitation of the basic right under Art. 13(1).
 2. The way in which Art. 13(3) was enacted was perfectly proper: …
 the amendment was supported by a two-thirds majority in both the Bundestag and the Bundesrat.
 3. The law also respects the substantive limits which the Constitution sets to constitutional amendments.
 a) Under Art. 79(3) of the Constitution no amendment may tamper with the basic principles laid down in Art. 1 and 20. These include not only respect and protection for individual human dignity (Art. 1(1)) but also the commitment to those inviolable and inalienable human rights which are the basis of any human society devoted to peace and justice (Art. 1(2)). The reference in Art. 1(3) to further basic rights involves that they also are immune to statutory restriction to the extent that they are essential to the maintenance of the values emanating from Art 1 and 2.
 Accordingly the essential principles of the Rechtsstaat and the social state, as expressed in Art 20(1) and (3), must also be respected.
 Art. 79(3) of the Constitution is an exceptional provision which must be narrowly construed: it does not preclude constitutional amendments which on proper substantive grounds modify existing legislative expressions of these principles. The Bundesverfassungsgericht rightly accepts that the Constitution may be amended in such a way as to modify, limit or even abolish basic rights provided that the basic principles laid down in Art. 1 and 20 are not affected. The lawmaker is free, if he has good reason for doing so, to modify the manner in which these principles are currently reflected in law.
 The rule that statutes must not affect the essential content of any basic right (Art. 19(2)) does not apply to laws which amend the Constitution. The only basic right which is protected against constitutional amendment by Art. 79(3) is the essential right of human dignity.
 b) Art. 13(3) is quite compatible with the guarantee of human dignity contained in Art. 1(1) of the Constitution.
 …Acoustic surveillance of domestic premises for the purposes of criminal investigation does not of itself constitute an infringement of the right of human dignity protected by Art 13(1) and 2(1) in conjunction with Art. 1(1) of the Constitution, but it may be conducted in such a manner as to compromise that right. Art. 13(3) contains specific provisions which are designed to prevent this, and they should be widely interpreted … Any laws passed thereunder must ensure that human dignity is not infringed in any individual case, for it is only such laws which are permitted by Art. 13(3). …
 (1) This court has frequently expressed the view that it is inconsistent with the dignity of the individual for the state to treat him as an object.
 This view, however, has its limits… The mere fact that a person is the object of criminal investigation does not prejudice his human dignity, but it may do so if the procedures adopted disregard his individuality as a person, if the conduct of the public power fails to show the consideration to which every individual is entitled in his own right. Such conduct is impermissible even when undertaken with a view to enforcing the criminal law or ascertaining the underlying facts.
 While even covert surveillance by the state does not of itself constitute an infringement of the individual’s unconditional claim to proper treatment… the central core of a person’s right to conduct his life must be respected as inviolable. … The central core of a person’s private life is absolutely protected, and its invasion cannot be justified in the public interest, even where its demands are powerful and pressing.
 (2) The protection of the worth of the individual is also instantiated in the basic right contained in Art. 13(1). The inviolability of the home is closely connected with the dignity of the individual and so is immediately related to the constitutional requirement that the exclusively private “highly personal” sphere of a person’s life be unconditionally safeguarded. When a person is at home, his right to be let alone must be especially assured.
 A person cannot develop his personality unless he is able to express his inmost sentiments and feelings, his opinions, reflections and experiences - including non-verbal manifestations of emotions and sexuality - free from any fear that state agencies may be listening in. Such self-development is possible only if there is a space in which these matters may be freely expressed. Confidential intercourse, equally necessary for personal development, also calls for space where the citizen can rely on the state’s protection, and this space is commonly the home from which strangers can be excluded. The individual who has such a space can use it for his private purposes as he chooses. The home is the “last refuge” for the protection of human dignity. This does not entail that the actual rooms in a home be protected absolutely, but that absolute protection be given to conduct of the individual therein when expressing and developing his most intimate self.
 (3) This protection must not be weakened by weighing it against the public interest in the prosecution of crime, even in the light of the principle of proportionality. It may well be that when there is cogent evidence that an extremely serious crime has been committed, many people would think the public interest in the effective repression of crime outweighs the dignity of the suspect. Nevertheless, the Constitution forbids the state to make any such evaluation (Art. 1(1), 79(3)).
 bb) Unless it respects the very core of private life acoustic surveillance of domestic premises for purposes of criminal investigation infringes the right of human dignity.
 Whether the inviolable core of private life is reached in a particular case depends on whether the situation has a highly personal character and also on the manner and the extent to which the life of others and the needs of society are affected . …
 cc) The power accorded to the lawmaker by Art. 13(3) to regulate acoustic surveillance of domestic premises validates only such regulations and implementing measures as conform with the limits of, and so do not infringe, Art. 79(3), read with Art. 1 (1). Art. 13(3) itself sets such limits and further constraints emerge from other constitutional rules, systematically interpreted.. …
 (1) There are both formal and substantive constraints on the legality of surveillance under Art. 13(3).
 Under the first sentence of that article acoustic surveillance is permissible only in pursuance of the very serious crimes specified in the Article and then only when the suspicion of guilt is based on specific facts. The crimes in question are typically those committed by members of organised groups of criminals….
 Then Art. 13(3) requires that the information sought be unobtainable by other means short of disproportionate effort. The new constitutional text itself thereby makes it clear that it is only as a last resort that acoustic surveillance is to be used in criminal investigation.
 From the procedural point of view the text respects these constitutional requirements by providing that any surveillance must be authorised by a temporary order issued by a three-judge court.
 (2) Certain restrictions other than those specified in Art. 13(3) must be respected by criminal investigators in the light of the absolute protection of the central zone of private life. These further restrictions, as is the case with all fundamental rights, emanate from other provisions of the Constitution. ..
 (a) The restrictions in the constitutional amendment must be interpreted in the light of other fundamental rights, especially Art. 1(1), and of the principle of proportionality.
 (b) Given that the amendment simply empowers the legislator to enact laws which sufficiently reflect the restrictions set by Art. 1(1), there is no stated criterion for determining when these limitations may have been exceeded. The principle of proportionality falls to be applied.
 dd) The legislative rules must be clear enough to prohibit any kind of acoustic surveillance which would infringe the dignity of the individual on domestic premises. No surveillance may be undertaken when there is reason to believe that individual dignity would be compromised by its use, and it must be terminated if it unexpectedly reveals information which is absolutely protected. Any record of such information must be destroyed and no use may be made of it in criminal proceedings.
 (1) Since even in his most intimate affairs the individual needs social relations in order to develop himself steps must be taken to protect an individual’s dignity not only when he is alone but also when he is consorting with others. One must therefore decide whether one is in the area of private self-development, which is inviolable, or in the social sphere, where state intrusion is sometimes permissible. Here it is not just a question of whether or not the occasion has some social aspect, but also what kind it is and how important.
 (2) Discussion of crimes already committed may or may not appertain to the inviolable core of private life. While statements in conversation which, for example, simply attest the inner thoughts and feelings of the speaker without reference to any actual crime do not thereby acquire a social quality just because they may relate to the causes or motives of criminal conduct, the social aspect does predominate when the talk is of a specific crime.
 (3) In order to avoid any invasion of the central core of private life there must be no listening in to conversations at home between the suspect and his closest confidants, such as family members or other intimates, unless there are objective grounds for supposing that they would directly concern criminal conduct. Of course not all such private conversations relate to the central core of private life, but in the interests of protecting human dignity it should be presumed that they do. Acoustic surveillance is barred whenever the conversations it might well disclose are absolutely protected.
 (4) Since it depends on the subject-matter of a conversation whether or not it is absolutely protected, one normally has to listen in to it before one can say whether it is about an essentially private matter or one which is merely social. Even so, the due protection of what is essentially private requires that such surveillance be undertaken only when there is objective reason to conclude that the conversation is not about something essentially private. …
 (a) Such a reason may be indicated by the nature of the premises in question.
 (a) Thus conversations in offices and business premises usually concern business and so are typically of a social nature… Yet conversations taking place there may well be essentially private affairs notwithstanding that the intimacy and seclusion of a dwelling are lacking, and if this can be ascertained in the particular case, then the protection must be absolute. …
 (ß) Conversations which occur in places to which people withdraw for private purposes may be presumed to be essentially private …
 (b) The probability that surveillance may infringe what is essentially private may depend on what third parties are present.
 A good indication of whether individual dignity is involved in a conversation is whether the persons present are strangers or people he particularly trusts, such as spouses and children, or possibly other close relatives such as siblings and ascendants, especially if they live there together. Here Art 6(1) and (2) of the Constitution are engaged, as well as Art. 13(1).
 The protection of what is essentially private also covers conversations with other confidants, such as close personal friends….
 Human dignity being one aspect of the freedom of religion guaranteed by the Constitution (Art. 4(1) and (2)), protection extends to the confessional and related speech. Human dignity also confers an entitlement to speak freely with one’s defence lawyer, for otherwise the accused could become a mere object of the criminal proceedings. Certain conversations with one’s doctor may have to be treated as essentially private. By contrast, the law which allows journalists and members of Parliament to refuse to disclose their sources has nothing to do with privacy: it is justified by the functional requirements of these institutions, not by the need to protect the privacy of the accused.
 (5) Where acoustic surveillance of private dwellings is in principle licit, it must be limited to conversations which probably have some relevance to criminal proceedings… This does not, however, justify entering the essentially private domain in order to ascertain whether or not that is the case.
 Continuous surveillance of a particular home is very likely to disclose essentially private conversations, and so is impermissible. Human dignity is also prejudiced if surveillance is so prolonged and comprehensive that a picture of the individual concerned can be built up from all his recorded movements and utterances.
 (6) In the absence of any indicia that absolutely protected conversations may be overheard, it is permissible to listen in to a suspect’s conversations in order to find out whether criminal proceedings would lie. With the above proviso, such a preliminary trawl is not constitutionally inconsistent with the protection of human dignity…
 If it transpires during surveillance that an essentially private matter is involved, the surveillance must be discontinued, and all records of it must be destroyed. Art. 13(3) must be interpreted as meaning that such records may not be used as evidence.
 The provisions in the Code of Criminal Procedure relating to acoustic surveillance of dwellings (§100c(1) no. 3, and §100(2) and (3)) and those relating to the collection and admissibility of evidence (§100 d(3)) are constitutional only in part, since they do not do full justice to the requirements of the protection of the inviolable area of private life (Art. 13(1) and (3) and Art. 2(1) of the Constitution, in conjunction with Art. 1(1)), or of the catalogue of relevant crimes or the general principle of proportionality.
 1. The constitutional standards that must be met by the provisions on acoustic surveillance in the Code of Criminal Procedure are primarily Art. 13(1) and (3) and also Art. 2(1) along with Art. 1(1) of the Constitution, which may interact with other fundamental rights, such as those under Art. 4(1) and (2) and Art. 6(1) and (2).
 a) The general right of personality, however, (emerging from Art. 2(1) conjointly with Art. 1(1)) is not relevant to invasions of residences…
 for it is a general provision which is ousted by the special provision of Art. 13(1) which specifically guarantees freedom from acoustic surveillance of private space… and covers, in addition to the actual surveillance itself, any necessary preliminaries and the subsequent processing of information and data thereby disclosed.
 b) But if the surveillance affects persons who cannot invoke the protection of art. 13(1) the general right of personality under Art. 2(1) along with Art. 1(1) is indeed engaged, for while every inhabitant or resident in a dwelling, regardless of the title by which they are there, enjoys the fundamental right under Art. 13(1), others who are just fortuitously present at the time can also be affected by the methods of surveillance. If the right of such persons is invaded, it is not the fundamental right under Art. 13(1), but the general right of human personality.
 c) The protection thus afforded to the privacy of the dwelling and the general right of personality may be supplemented in a particular case by further fundamental rights: conversations between spouses in their own home, for example, are protected not only by Art. 13(1) but also by Art. 6(1) of the Constitution.
 2. …..(a) The fundamental right to the inviolability of the dwelling covers not only physical intrusions and the introduction therein of technical equipment but also the use of devices for eavesdropping on what is going on there; it also extends to the storage, use and transmission of the information thereby obtained. …
 … This does not apply when what is happening inside the dwelling is naturally audible outside it, for while one’s privacy is doubtless affected whenever what one says is overheard, it is not protected by Art. 13, since, far from using his premises for the protection of his privacy, the party affected is himself the cause of his being overheard.
 3. The legislative texts which permit the use of acoustic surveillance for purposes of criminal investigation are constitutional only in part.
 a) Such texts must lay down measures which are sufficient to render it unlawful to invade the absolutely protected central core of private life. …. §100 d (3) of the Code of Criminal Procedure does not meet this requirement…
 (b) in as much as it fails to preclude surveillance when the suspect is in the company of close family members or specially trusted friends whom there is no reason to suspect;
 furthermore, as to those who are entitled to refuse to act as witnesses, a group which includes very close relatives, it does not prohibit surveillance but only precludes the disproportionate use of their evidence, and offers no protection at all to conversations with closely trusted friends who fall outside that group.
 Nor is sufficient protection for conversations with trusted friends sufficiently protected by the second sentence of §100d(3), which renders surveillance illicit if it is foreseeable that no part whatever of the information gathered may be lawfully used …  for this is hardly ever the case when the only people in the home with the suspect are his close relatives and intimates.
 bb) Nor does §100d(3) of the Code of Criminal Procedure make sufficient provision for the termination of the surveillance if it unexpectedly emerges that the inviolable central core of privacy is involved. In such cases it is unlawful to continue the surveillance.
 cc) Nor do the rules sufficiently prevent the use of information obtained from the central zone of private life or require the destruction of data already acquired.
 (d) Doubtless the prohibition of the use and the retention of such data can be inferred from the Constitution itself, but this does not mean that legislation is superfluous: the legislator’s role is to spell out the constitutional texts, and in doing so he has a certain room for play which the courts must respect. Some gaps can be filled, in part at any rate, by the analogical application or §100d(3) and (6) of the Code of Criminal Procedure or by appropriate interpretation consistently with the Constitution. But beyond this the legislator must act.
 b) The permissibility of acoustic surveillance, provided always that it does not invade the absolutely protected central area of private life, depends on the application of the principle of proportionality… The rules in question do not quite meet its requirements. Certainly their aim is legitimate (aa) and the means adopted is appropriate to that end (bb) as required (cc). But whereas Art. 13(3) permits acoustic surveillance of domestic premises only where particularly serious crimes are suspected, §100c(1) no. 3 of the Code of Criminal Procedure is rather wider. In other respects the powers granted by the legislator, if narrowly construed, are constitutionally unobjectionable (ee).
 aa) In granting the power to conduct acoustic surveillance the legislator sought both to reveal the commission of serious crimes and to improve the way the law can combat organised crime. This purpose is constitutionally unobjectionable.
 bb) Acoustic surveillance under §100c(1) no. 3 of the Code of Criminal Procedure is well-adapted to the revelation of the crimes listed therein.
 A law is well-adapted to its purpose when it helps to achieve its aim. The legislator has some room for play in predicting its effect and in evaluating the dangers to which the public is exposed….
 cc) Since there seems to be no way of achieving this aim which is less invasive of fundamental rights, this law is also necessary…
 (1) … The court has only a limited ability to monitor the exercise of the judgement which the lawmaker is bound to use in determining whether the chosen method is necessary for the achievement of the aim …
 dd) As regards the principle of proportionality it is only in respect of especially serious crimes that the constitutional amendment allows the use of acoustic surveillance, provided always that it leaves intact the absolutely protected central core of private life, (Art. 13(3)). The list of crimes in §100c(1) no. 3 is not so restricted and is therefore unconstitutional….
 The travaux préparatoires clearly show that the legislator realised that only in the case of especially serious crimes was the grave invasion of the fundamental right under Art. 13(1) justifiable. This was not fully reflected in the text ultimately adopted. It is not clear what criterion of selection was used in drawing up the list of crimes and misdemeanours in §100c(1) no. 3 of the Code of Criminal Procedure: they vary in terms of both the interest affected and the degree of mens rea required.
 (1) The seriousness of an offence turns on the importance of the interest it infringes and other factual features relating to its commission and consequences.
 (a) The “especially serious crimes” referred to Art. 13 (3) must clearly be offences of more than average criminality.
 (c) Art. 13(3) does not constrain the legislator to list only such crimes as are typically committed by organised criminals, but. …
 crimes cannot be treated as especially serious just because they are characteristic of organised crime, for organised criminals can commit minor crimes as well as major ones.
 (a) … In determining which crimes are so serious as to justify the use of acoustic surveillance the legislator has some width of choice. Under Art. 13(3) the crime must, abstractly defined, be a very serious one. One useful indicator is the sentence prescribed: unless the maximum penalty laid down by law exceeds five years imprisonment one can assume that a crime is not very serious ….
 ee) In other respects, the powers contained in the legislation, provided it is construed narrowly, satisfy the requirements of Art. 13(3) and the strict principle of proportionality.
 (1) There is a tension between the state’s duty to adopt a criminal procedure which befits a Rechtsstaat and its duty to respect the constitutional rights not only of those inculpated and but also of third parties. The first task of the legislator is to seek to achieve a principled reconciliation of these conflicting values. When it comes to interpreting and applying the rules which restrict fundamental rights the courts must satisfy themselves that the outcome in the particular case is appropriate and fair, as must the authorities which execute the measures of surveillance.
 (2) Leaving aside its overextensive list of crimes, there is no constitutional objection to §100 c (1) no. 3 of the Code of Criminal Procedure, narrowly construed.
(a) §100 c (1) no. 3 lays down the requisite degree of suspicion. This is constitutionally acceptable.
 Under this provision acoustic surveillance of domestic premises is permissible if the suspicion of the commission of a serious crime is confirmed by “established facts”.
 Such a suspicion must be more firmly grounded than is needed for a mere initial suspicion of complicity, but not so convincingly as is needed for the “sufficient” or “compelling” suspicion laid down in other provisions of the Code. … The suspicion here must be based on actual, ideally mutually confirmatory, facts. ..
 The suspicion required to justify acoustic surveillance may fall well short of that needed before instituting proceedings (§170(1) Code of Criminal Procedure), or continuing them (§203) or arresting a person for purposes of investigation (§112(1)(1)), for the very purpose of the surveillance is to ascertain whether so cogent a suspicion is well-based.
(4) §100c (1) no. 3, §100c (2) sent. 4 and 5, and §100c (3), if restrictively interpreted, will ensure that acoustic surveillance of domestic premises does not affect third parties, not themselves under suspicion, more than is fair in relation to the public interest in make the criminal investigation effective, though of course any surveillance of third parties is wholly precluded if it reaches matters relating to the central core of private life.
 (α) Acoustic surveillance of domestic premises is a particularly grave invasion of a fundamental right, for it can seriously affect persons who have nothing to do with the crime under investigation , whose conduct has not in the least conduced to the invasion but who just happen to be close to the suspect or staying in the same house….
 (β) Covert surveillance of private conversations in homes can have an adverse effect not only the individual but on social intercourse in general. If the rules in force at the time permit the secret surveillance of those not suspected of anything, the very possibility of such eavesdropping can have a chilling effect. Free conversation is inhibited by the fear of being overheard.
 (b) The rules of law put forward are adequate to meet the constitutional requirements of limiting the invasive effect of surveillance on third parties.
 (α) It cannot be inferred from the restriction which is imposed by §100c (1) no. 3 of the Code of Criminal Procedure on the surveillance and recording of words spoken in private by the suspect that the restriction applies also to what third parties say, for otherwise the surveillance could not be carried out at all when the suspect was conversing with third parties. It does, however, indicate that in the home of the suspect only those conversations in which he himself takes part may be listened to.
 (β) The possibility of including in the surveillance the home of a third party not suspected is fairly covered by §100c(2) sent. 5 of the Code.
 …That provision emphasises the subsidiarity of such surveillance: it is not enough that the suspect be present in the home of the unsuspected third party, but it must in addition be sufficiently likely that the surveillance will disclose information relevant to a prosecution.
 Art. 13(3) of the Constitution in its third and fourth sentences provides for a degree of prior control of acoustic surveillance of domestic premises by an independent and neutral body, a court ..
 Judicial involvement here is in two respects more significant than in the case of searches (Art. 13(2)): the judicial authorisation must in principle come from a court of three judges (third sentence), and an order by a single judge is possible only in the case where delay would be dangerous (fourth sentence).
 (aa) … The court must state in sufficient detail its reasons for issuing the order, which must be as detailed as possible and practicable enough to ensure that the invasion of the fundamental rights be measurable and controllable.
 bb) The legislation adequately answers these requirements.
 b) Since the mode and operation of the surveillance are to be determined by law, the courts are entitled to give the authorities periodic instructions and in appropriate cases to intervene, so as to make sure that the inviolable core of privacy is not invaded and that the operation remains proportionate.
 3. There is nothing constitutionally objectionable about the period of four weeks which the legislator has set as the maximum duration of the judicial order of authorisation (§100 d (4) sent. 1 of the Code of Crimianl Procedure, pursuant to Art. 13(3) sent. 2 of the Constitution)….
 Art. 13(3) does not prohibit prolongation of the order. …
 Neither Art 13(3) of the Constitution nor the Code of Criminal Procedure specifies any absolute limit beyond which no prolongation is possible, but in a particular case the principle of proportionality might have that effect, since the longer the surveillance of domestic premises lasts, the more invasive it becomes and can indeed lead to a breach of the right of human dignity under Art. 13.
 As to informing the subjects of acoustic surveillance of the fact, the provisions laid down by §101 of the Code of Criminal Procedure are only partly reconcilable with Art 19(4) and 103 (1) of the Constitution.
 1. §101(1) of the Code of Criminal Procedure provides in its first sentence that there is no need to inform those affected if informing them could endanger public security or inhibit the further use of a mole. The second sentence provides that a court may decide to withhold information for six months after the surveillance has come to an end. This is procedurally insufficient to meet the constitutional duty to inform. …
 When secret invasions of fundamental rights by the state take place, the effective protection of those rights requires that the party affected be informed of them after the event.
 aa) In so far as it provides that information about acoustic surveillance need not be given if giving it would prejudice the investigative enterprise or endanger any person’s life and limb §101(1) of the Code of Criminal Procedure is not constitutionally objectionable
 bb) But its provision that silence about past acoustic surveillance may be maintained just because disclosure could prejudice public security or the continued use of a mole is not consistent with Art. 13(1) and Art. 19(4) as well as Art. 2(1), read with Art. 1(1) of the Constitution.
 (1) The concept of “public security” chosen here by the legislator is widely used in police laws with a very wide coverage, extending sometimes to all the interests protected by law. However, it is not all legal interests whose protection justifies a failure to inform: the law must be more specific and state which of the legally protected interests are important enough to justify the deferral or even suppression of the duty to inform of secret invasions of fundamental rights. This has not been done.
 (2) The refusal to disclose past acoustic surveillance is not justified by the consideration that disclosure could make it impossible to continue to use a secret informant.
 Of course it is enough if the discontinuation of the use of the informant inhibited the discovery of the facts by other means, but this is already covered by the rule that the investigative enterprise must not be thwarted. And in so far as the legislator was concerned with the physical security of the mole and his associates, that, too, is covered by the justification dealt with in aa) above. Apart from such cases, the continued use of a secret informant is an insufficient justification.
 2. §100 d (5) sent. 2 and §100 f (1) of the Code of Criminal Procedure allow the thrust of the investigation to be altered in the light of the information about individuals acquired through the acoustic surveillance. In themselves these are not constitutionally objectionable.
 a) It is true that the purpose and methods of the surveillance determine whether or not it is proper to retain and use personal information and data acquired thereby. The use of such information for a purpose other than that originally entertained constitutes in itself a separate invasion of a fundamental right, since the protection afforded by Art. 13(1) of the Constitution covers the transmission of such information as well as its acquisition inside and outside the dwelling.
 Of course the principle that the purpose is controlling does not mean that it cannot be changed, but for this there must be a statutory basis which is both formally and substantially in accordance with the Constitution. …
 b) The rules which are now being questioned do in themselves satisfy these requirements.
 3. However, the law imposes no duty to label or identify the data acquired by acoustic surveillance. This means that the provisions regarding the further use of such data are inconsistent with Art. 13(1) and Art. 2(1) read with Art. 1(1) of the Constitution.
 The only way one can prevent information being used for purposes other than that of the surveillance is by making it possible to identify the data so acquired. The Constitution therefore requires an appropriate method of identifying them, for otherwise the data acquired by the surveillance could be mixed up in storage with other data in such a way that their source could no longer established.
 §100 d (4) sent. 3 and §100 b(6) of the Code of Criminal Procedure relate to the destruction of data: they are inconsistent with Art. 19(4) of the Constitution. …
 The protection of Art. 13(1) extends to the processing of data lawfully acquired, and requires that they be destroyed as soon as they are no longer necessary for the authorised purpose. The rules relating to their destruction must also meet the dictates of the principle of effective protection. … This being so, the duty to destroy the data must be so clearly specified that in cases where the affected party seeks judicial review of the methods of processing information and data the protection of his rights is not thwarted or evaded.
 In a claim against the authorities by any affected party with a presumptively serious interest in the protection of his rights, including the right to have his information protected, this can be done by blocking the information so that it cannot be used for any purpose except that of informing the party himself or permitting judicial control. …
(Judges Jaeger and Hohmann-Dennhardt)
 We dissent from the majority opinion given at C I above . In our view the amendment contained in Art. 13(3) is incompatible with Art. 79(3) of the Constitution and therefore void. …