Electronic Monitoring in Pre-Trial Detention: Section 173a StPO, House Arrest with Ankle Tag in Austria

§ 173a StPO bears the heading “House arrest” and was inserted into the StPO in 2010 by the Criminal Procedure Amendment Act (BGBl I 2010/64). It has been in force unchanged since 01.09.2010. Paragraph 1 of the section provides: “On application by the public prosecutor or the accused, pre-trial detention may be continued as house arrest, to be executed in the accommodation in which the accused has established a domestic residence.”

First prerequisite, domestic residence. The accused must have accommodation in Austria in which house arrest can actually be executed. Under § 66 of the Jurisdiction Act (JN), residence is the place at which the accused has settled with the intention of taking up permanent abode there; mere police registration is not sufficient (OGH 14 Nds 73/02). The accommodation must also be "suitable in light of the grounds for detention" (Explanatory Memorandum 772 BlgNR 24th legislative period, 9). Accommodation owned by a co-suspect, accommodation without stable mobile reception or accommodation that also houses several trial witnesses is regularly ruled out.

Second prerequisite, settled living conditions. Stability in housing, employment and social ties. The probation service (NEUSTART) reports to the court on these living conditions, agrees the concrete conditions of the house arrest with the accused and lays down the result in a social report for the detention hearing. Without this social report the court typically does not decide.

Third prerequisite, consent to electronic monitoring. The accused must formally consent to being monitored by suitable means of electronic supervision. § 173a Abs. 1 StPO refers in technical terms to § 156b Abs. 1 and 2 of the Execution of Sentences Act (StVG), the legislature points to that provision because the monitoring technology was first regulated in the field of executing sentences. Consent may be withdrawn at any time; a withdrawal leads, under § 173a Abs. 4 sentence 1 StPO, to the mandatory termination of house arrest.

Fourth prerequisite, formal undertaking. At the detention hearing the accused expressly affirms that he or she will comply with the conditions agreed with the probation service. This undertaking is not merely formal, its breach is, under § 173a Abs. 4 sentence 2 StPO, one of the classic grounds for revocation.

Two further substantive conditions are added to the first and second prerequisites: pre-trial detention must not be capable of being lifted through less intrusive measures under § 173 Abs. 5 StPO, while at the same time the purpose of detention under § 182 Abs. 1 StPO must remain attainable in this special form of execution. House arrest is therefore the second line: first the less intrusive measures are examined, then, if these are not sufficient, house arrest. House arrest is not a less intrusive measure within the meaning of § 173 Abs. 5 StPO, but a special form of executing the still-upheld pre-trial detention (so expressly OGH 12 Os 102/17t and 15 Os 165/10v; Kirchbacher/Rami in Fuchs/Ratz, WK StPO § 173a, as at 01.01.2025, marginal no. 1). The heading of § 173a and its para 1 first sentence use the term "house arrest", which the prevailing view regards as euphemistic; only the electronically monitored house arrest is permissible. Execution of pre-trial detention as house arrest without electronic monitoring is ruled out from the outset.

In practice, Kirchbacher/Rami note: "It is practically conceivable only in rare cases that the purposes of pre-trial detention can also be achieved through electronically monitored house arrest" (WK § 173a marginal no. 4). Where a ground for detention exists and less intrusive measures do not suffice, the same risk can, as a rule, not be effectively countered by house arrest either. Roland Kier, in his handbook chapter, speaks of "particular reservations on the part of detention judges" towards this form of execution (Kier in Kier/Wess, HB Strafverteidigung Kap 9, as at 01.05.2022, marginal no. 9.65). From the defence perspective this means that the application must be especially carefully prepared in order to have any prospect of success.

An application for house arrest may be made by the accused and the prosecution. At any time, the accused may make that application under § 174 Abs. 3 Z 8 StPO. At a detention hearing, which must be scheduled without delay under § 176 Abs. 1 Z 2 StPO, the competent court decides under § 173a Abs. 2 StPO. During the investigation, jurisdiction is held by the single judge of the Regional Court under § 31 Abs. 1 Z 2 StPO. After the indictment is filed, the jurisdiction rules for the main proceedings apply.

The most important clarification at the outset: § 173a StPO and § 156b StVG are not the same. Both norms regulate an electronically monitored house arrest with an ankle tag, but they apply in entirely different phases of the proceedings, under different prerequisites and with different legal consequences.

§ 173a StPO is a particular form of executing pre-trial detention. It operates before the final conviction, in the investigation and main trial phase, and presupposes that pre-trial detention as such would be upheld (strong suspicion plus a ground for detention) but can be executed outside the prison. The accused remains legally in pre-trial detention; only the place of execution changes from the prison to the accused's own accommodation.

§ 156b StVG: Electronically monitored house arrest under § 156b StVG constitutes a form of sentence enforcement following final conviction. § 156c StVG sets forth the time-related approval requirements: as a general rule, the sentence to be served or remaining must not exceed 24 months, whereas specified convictions are subject to a twelve-month limit. Consideration must also be given to the statutory forecast concerning the remaining sentence. § 156b Abs. 3 StVG governs the reimbursement of costs and its limits.

The Supreme Court expressly clarified this distinction in 2010: Austrian Supreme Court (OGH) 15 Os 165/10v of 23.12.2010 (legal proposition RS0126401). The OGH there formulated that house arrest under § 173a StPO is “a particular form of executing pre-trial detention and not an alternative to pre-trial detention”. From this it follows that, for an order of house arrest, all prerequisites of pre-trial detention under § 173 StPO must be present, in particular strong suspicion and a ground for detention under § 173 Abs. 2 StPO. Anyone applying for house arrest without attacking these prerequisites leaves the most important line of defence unused.

A fundamental-rights complaint may challenge continued pre-trial detention as house arrest under OGH case law, and refusal of this form of detention alone falls outside that remedy's scope. For an ordinary complaint, the subject and notification of the particular decision must be checked: § 88 Abs. 1 StPO provides fourteen days from notification, while § 176 Abs. 5 StPO provides three days from pronouncement for an order under its Abs. 4. Where an order both continues detention and refuses house arrest, those affected must not assume that the period starts only on later service, and defence counsel should check the deadline immediately against the order.

Technically, § 173a Abs. 1 StPO does refer to § 156b Abs. 1 and 2 StVG, but that concerns only the means of monitoring (ankle tag, electronic supervision). The legal consequence remains different: in the case of § 173a, pre-trial detention; in the case of § 156b, execution of sentence. Anyone confusing the two risks applying the wrong norm and, with it, the wrong examination of the prerequisites.

Electronic monitoring in house arrest comprises three components, a transmitter on the body, a receiving unit in the accommodation and the prison's monitoring centre. Each component fulfils its own function and is coordinated with the others.

Transmitter on the body. An electronic ankle tag, a waterproof bracelet worn at the ankle, with a built-in radio transmitter and tamper sensor. The bracelet is designed so that any attempt to cut, open or remove it is immediately detected and reported to the monitoring centre. It is drip- and shower-proof and is deliberately not removed in everyday life.

Receiving unit in the accommodation. A stationary base station installed in the accused's home. It communicates via the mobile network with the prison's monitoring centre and reports the presence or absence of the transmitter within a defined radio zone. If the accused leaves this zone outside the permitted time windows, an alarm reaches the centre. Stability of mobile reception is therefore a technical suitability requirement for the accommodation, if reception is patchy, house arrest fails on the hardware alone.

GPS component. Some devices additionally provide a location function outside the radio zone, for example for the journey to the workplace or to medical treatment. § 156b Abs. 1 StVG, to which § 173a Abs. 1 StPO refers in technical terms, speaks generally of “suitable means of electronic supervision” without fixing the technology. The current state of the art therefore remains applicable; the concrete hardware and configuration are coordinated between the prison, NEUSTART and the accused.

The technical operation of the system is the responsibility of the prison. It sets up the hardware, maintains it, responds to alarms and, where there is reasonable suspicion, orders an inspection. The social support runs in parallel via NEUSTART, the probation service accompanies the accused during the house arrest, monitors compliance with the conditions and reports back as soon as problems become apparent.

Under § 173a Abs. 3 StPO, the set-up follows a clearly regulated sequence: if the house arrest application is granted, the public prosecutor notifies the criminal police and the security authority of the place of residence. The prison sets up the technical means of electronic supervision. Only once the equipment is in place is the accused transferred from the prison to house arrest. A certain lead time can therefore elapse between the court's decision and the actual move into house arrest, counsel and relatives should be aware of this and factor it into expectation management.

House arrest is not release, it remains pre-trial detention, only in a more lenient form of execution. From this follows a clearly delineated catalogue of obligations, the breach of which under § 173a Abs. 4 sentence 2 StPO counts among the classic grounds for revocation.

Duty to remain in the accommodation. In principle, the accommodation may not be left. § 173a Abs. 2 last sentence StPO lists the permitted reasons for leaving exhaustively: reaching the workplace or place of training, procuring necessary daily necessities and obtaining necessary medical assistance, in each case by the shortest route. Other routes are not permissible: leisure activities, sport, visits to relatives, club meetings, restaurant visits, walks without a specific purpose. During the non-released times the accused is present in the accommodation.

Specification through the formal undertaking. Precisely which working or training hours are permissible, on which days daily necessities may be procured and which doctors may be consulted is governed by the individual agreement with the probation service. These conditions are recorded in the social report and the accused affirms them by formal undertaking at the detention hearing (§ 173a Abs. 2 sentence 2 last half-sentence StPO). From that moment the undertaking is binding, deviations trigger alarms in the monitoring centre.

Toleration of electronic monitoring. The accused wears the ankle tag continuously, accepts the radio monitoring in the accommodation and, where applicable, the GPS location on permitted routes. Any attempt to manipulate the transmitter triggers an alarm and counts as a breach. Leaving the accommodation outside the permitted times or routes is likewise detected immediately by the monitoring centre.

Cooperation with NEUSTART. Throughout the duration of the house arrest, the accused is obliged to maintain contact with NEUSTART, keep appointments, comply with reporting and cooperation duties, report changes in living circumstances (loss of employment, change of accommodation, new medical treatment). The probation service is therefore not merely the source of the prior report, but a continuing point of contact during the execution.

Maintenance of consent. § 173a Abs. 1 last sub-clause StPO makes the accused's consent to electronic monitoring a constitutive prerequisite. This consent may be withdrawn at any time, § 173a Abs. 4 sentence 1 StPO links to it the mandatory termination of the house arrest. A withdrawal of consent is therefore effective, but has a clear consequence: the accused is transferred back to the prison and pre-trial detention continues there as ordinary custodial detention.

Cost implications. No costs are payable for house arrest during pre-trial detention, according to the Ministry of Justice. Instead, § 156b Abs. 3 StVG governs cost contributions during sentence enforcement. Crediting time already spent in detention and the transition at finality are separate questions: if house arrest has not been revoked, § 173a Abs. 5 StPO refers to § 3 Abs. 2 StVG for the consequence of finality. Separate approval is required for continued detention at home under §§ 156b ff StVG.

Consequences for detention hearings and detention orders. Upon the ordering of house arrest, § 173a Abs. 1 StPO removes automatic detention hearings, and an order continuing or lifting pre-trial detention may be issued in writing without a prior oral hearing. The other rules apply correspondingly. The procedural stage matters: § 178 Abs. 1 StPO limits detention before the main trial begins. After indictment, a detention order is no longer limited by the detention-review period under § 175 Abs. 5 StPO. Detention grounds and proportionality must still be reviewed after a first judgment.

§ 173a Abs. 4 StPO lists the grounds for revocation exhaustively. Anyone, whether relative or counsel, who wants to safeguard the house arrest should know them; every breach can lead to a return to custodial detention.

First ground: withdrawal of consent by the accused. § 173a Abs. 4 sentence 1 StPO provides that, where the accused declares that he or she withdraws consent, the court is to revoke the house arrest and order the continued execution of pre-trial detention in the prison. The revocation takes place of the court's own motion, no application by the public prosecutor is required. In practice this rarely occurs, because the accused has typically fought for the house arrest and wants to keep it. Where it does happen, it is mostly for personal or family reasons that are no longer compatible with execution in the specific accommodation.

Second ground: breach of the formal undertaking. § 173a Abs. 4 sentence 2 first half-sentence StPO provides that, on the application of the public prosecutor, the court revokes the house arrest where the accused, contrary to the undertaking, does not comply with the conditions. Classic configurations are unauthorised leaving of the accommodation outside permitted times or routes, frequenting prohibited places or persons, breach of abstinence requirements in the case of substance conditions, or contact with co-suspects or witnesses contrary to a contact ban fixed in the undertaking.

Third ground: purposes of detention no longer attainable. § 173a Abs. 4 sentence 2 second half-sentence StPO forms the catch-all provision. It applies where, for external reasons, the purposes of detention under § 182 Abs. 1 StPO can no longer be attained in house arrest, for example through new collusion activity, manipulation of the ankle tag or new commission of offences during the execution. Loss of suitable accommodation (termination, loss of the home) and serious technical failure scenarios also fall under this provision. A revocation under sentence 2 requires an application by the public prosecutor.

Legal consequence of revocation. § 173a Abs. 4 sentence 3 StPO provides that the transfer is to be entrusted to the criminal police. The accused is therefore brought back to the prison directly; pre-trial detention continues there as ordinary custodial detention. The time spent in house arrest so far counts as pre-trial detention time and is credited against the sentence in the event of a later conviction.

What relatives and counsel should take away from this: house arrest is winnable, but fragile. Every breach of the undertaking, even one that appears minor, can trigger revocation. Anyone living in house arrest should therefore, in case of doubt, interpret the conditions more restrictively than necessary and, in case of doubt, consult the probation service. In a conflict between a permitted route and a personal need, the narrower interpretation is safer than the broader one, the cost of revocation outweighs the personal convenience of a single errand.

From the experience of detention defence, three configurations can be identified in which the house arrest application has particularly good prospects, together with the typical refusal grounds that cause the application to fail.

Promising: pure risk of flight without foreign ties. The classic main case of § 173a StPO. The accused has a settled domestic residence, an existing employment relationship and stable social ties locally. The asserted risk of flight is the only supporting assumption of pre-trial detention, it is defused directly by the ankle tag's binding to the accommodation, because every unauthorised movement is reported at once. In this configuration the house arrest application has the highest prospect of success.

Promising: white-collar cases with longer proceedings. File study, balance sheet and expert-report proceedings often stretch over months. White-collar cases are structurally favourable for § 173a, the accused regularly has settled living conditions and a professional environment compatible with house arrest. The risk of collusion can be reduced through clear conditions, email and telephone restrictions, contact bans for co-suspects, separation from operational company management. Anyone presenting the court with a detailed package of conditions proactively neutralises the most common refusal ground.

Promising: care duties and child care. Where the accused is responsible for the care of minor children, the proportionality argument operates in favour of the more lenient form of execution. The logic: prolonged custodial detention affects not only the accused but also the children involved; house arrest allows the continuation of childcare and is therefore the milder means within the same execution goal. § 156b Abs. 1 StVG recognises child care as equivalent to gainful occupation, that assessment carries over through the linking provision in § 173a Abs. 1 StPO.

Arguments that convince at the detention hearing. Three points raise the success rate in practice: first, request the probation service's social report as early as possible, ideally before the detention hearing; § 179 StPO allows provisional probation supervision in advance. Second, offer concrete conditions, workplace with fixed hours, medical treatment, addiction therapy where applicable. The more concrete, the more likely the court will follow. Third, document the technical suitability of the accommodation, mobile reception, adequate room layout, no co-suspects or aggrieved persons in the household.

Common refusal grounds. First: no suitable accommodation, no domestic residence, precarious housing, accommodation owned by a co-suspect. Second: risk of flight through foreign ties, multiple citizenships, family abroad, international business activity, only a short prior stay in Austria. Here the court typically assumes that the spatial binding to the accommodation does not sufficiently control the risk of flight, because the ankle tag only reports movement rather than physically preventing it. Third: risk of collusion through co-suspects in the household, family constellations, partners as co-suspects, trial witnesses in the immediate environment. Fourth: substance problems without stable therapeutic support, house arrest without a therapy link is regarded as too uncertain in prognosis.

Relationship with § 173 Abs. 5 StPO. A central rule of practice: before any house arrest application it must be examined whether pre-trial detention can be replaced at all by less intrusive measures under § 173 Abs. 5 StPO, formal undertaking to attend, passport deposit, residence condition, reporting duty, contact bans, abstinence requirements. § 173a StPO is only the second line, where less intrusive measures are not sufficient but the purpose of detention remains attainable outside the prison. Anyone applying for house arrest without offering the less intrusive measures in parallel leaves the milder instrument unexamined, the court will regularly notice.

Link to the mandatory hearing under § 174 StPO. In practice the house arrest application is announced as early as the first mandatory hearing or filed at the latest at the first detention hearing. Early filing is central, because the probation service needs several days of lead time to complete the social report. Anyone filing the application two weeks later loses valuable time, pre-trial detention continues in the prison in the meantime. More on the mandatory hearing in our article on strong suspicion.