From October 2010 until March 2012, a pilot project on electronic monitoring electronic monitoring occurred in the German state of Baden-Württemberg. In conjunction with this project, the Max Planck Institute carried out an empirical study to evaluate this pilot project, including its implementation, acceptance, and the psychosocial effects of EM. A follow-up study analyzed recidivism rates among prisoners who participated in the pilot project (follow-up: 3 years).

Ob­ject of re­search

In Ju­ly 2009, the state par­lia­ment of Baden-Württem­berg passed the “Act on elec­tron­ic mon­it­or­ing dur­ing the en­force­ment of im­pris­on­ment”; this cre­ated a leg­al frame­work for the im­ple­ment­a­tion of elec­tron­ic mon­it­or­ing. The Act ex­pired in Au­gust 2013. The Act en­abled elec­tron­ic mon­it­or­ing to take place in the fol­low­ing three in­stances:

  • To facilitate home detention as a substitute for imprisonment for failure to pay a fine,
  • To prepare prisoners for release towards the end of a sentence, and 
  • To support privileges, such as supervised work release.

Re­search ques­tions

The re­search pro­ject in­vest­ig­ated wheth­er elec­tron­ic mon­it­or­ing had an ef­fect on the reso­cial­iz­a­tion of re­leased pris­on­ers, wheth­er it ex­er­ted the ex­pec­ted ef­fect of avoid­ing im­pris­on­ment (es­pe­cially when used as a sub­sti­tute for im­pris­on­ment), and wheth­er it con­tin­ued to ex­ert an ef­fect on those who par­ti­cip­ated in its use with re­gard to re­cidiv­ism. Thus, the over­all aim of the re­search pro­ject was to de­term­ine wheth­er elec­tron­ic mon­it­or­ing is a worth­while al­tern­at­ive sanc­tion for cer­tain tar­get groups.


An ex­per­i­ment­al design was used to in­vest­ig­ate the above­men­tioned re­search ques­tions. The sub­jects – who came from five dif­fer­ent pris­ons in Baden-Württem­berg – were ran­domly as­signed to an ex­per­i­ment­al group (whose sub­jects could par­ti­cip­ate in the elec­tron­ic mon­it­or­ing tri­al) and a con­trol group (where reg­u­lar pris­on sen­ten­cing prac­tices were ap­plied). In­di­vidu­al­ized cor­rec­tion­al pro­grams were cre­ated for sub­jects in the ex­per­i­ment­al group, in­clud­ing the es­tab­lish­ment of defined con­tain­ment zones; their com­pli­ance was then mon­itored via GPS tech­no­logy. Vi­ol­a­tions were auto­mat­ic­ally trans­mit­ted to a tech­nic­al cen­ter, which in turn in­formed the re­spons­ible pris­on au­thor­it­ies to ini­ti­ate fur­ther steps. In the case of elec­tron­ic mon­it­or­ing with house ar­rest, su­per­vi­sion by pro­ba­tion ser­vice of­ficers was an in­teg­ral part of the over­all concept. Par­ti­cip­a­tion in the pi­lot pro­ject was only pos­sible for those sub­jects who met cer­tain pre­con­di­tions, in­clud­ing, for ex­ample, a min­im­um of four hours em­ploy­ment per day (or an equi­val­ent activ­ity). In ad­di­tion to in­vest­ig­at­ing the sub­jects in the ex­per­i­ment­al and con­trol groups, oth­er rel­ev­ant par­ti­cipants in the pro­ject were in­ter­viewed (e.g., pro­ba­tion of­ficers, pub­lic pro­sec­utors, pris­on em­ploy­ees).

Im­ple­ment­a­tion and psychoso­cial ef­fects

The first phase of the pi­lot pro­ject in­vest­ig­ated the psychoso­cial and pre­vent­ive ef­fects of elec­tron­ic mon­it­or­ing, as well as its po­ten­tial to as­sist reso­cial­iz­a­tion (see Schwedler & Wößn­er, 2015, Schwedler & Woess­ner 2017).

The planned num­ber of 150 par­ti­cipants in the pi­lot pro­ject was not reached: a total of 92 took part. The use of elec­tron­ic mon­it­or­ing as a sub­sti­tute for im­pris­on­ment (in cases a fine could not be paid) failed com­pletely, with only one suit­able sub­ject. The reas­on for this was that sub­jects who could not pay a fine usu­ally did not meet the con­di­tions for par­ti­cip­a­tion in the pi­lot pro­ject.

All sub­jects who were pro­posed for in­clu­sion in the pi­lot pro­ject dis­played com­par­at­ively high func­tion­al levels in those areas where elec­tron­ic mon­it­or­ing was ex­pec­ted to have an ef­fect (see Schwedler & Wößn­er 2015). Most of the sub­jects had no dif­fi­culty in find­ing work, were so­cially in­teg­rated, and showed psy­cho­met­ric test res­ults that were com­par­able to the norm­at­ive samples of these in­stru­ments. At the same time, the sub­jects were low-risk pris­on­ers. A minor ef­fect of elec­tron­ic mon­it­or­ing was able to be found con­cern­ing a re­duc­tion in the pris­on­iz­a­tion ex­per­i­ence.

A quarter of the sub­jects felt that the ex­per­i­ence of elec­tron­ic mon­it­or­ing was psy­cho­lo­gic­ally stress­ful and about two-thirds re­por­ted phys­ic­al com­plaints con­cern­ing the GPS ankle brace­lets. Nev­er­the­less, the meas­ure met with an over­all pos­it­ive re­sponse amongst al­most all sub­jects, which must however be in­ter­preted in com­par­is­on with the al­tern­at­ive op­tion of reg­u­lar de­ten­tion. On the whole, elec­tron­ic mon­it­or­ing lagged be­hind the ex­pect­a­tions of the pi­lot pro­ject and did not live up to its ex­pec­ted po­ten­tial, both in terms of de­ten­tion and re­hab­il­it­a­tion.

Ana­lys­is of post-mon­it­or­ing re­cidiv­ism

To meas­ure post-mon­it­or­ing re­cidiv­ism, of­fi­cial data from the Fed­er­al Cent­ral Crim­in­al Re­gister were ob­tained and eval­u­ated. Re­cidiv­ism rates between the two com­par­is­on groups (ex­per­i­ment­al vs. con­trol) did not sig­ni­fic­antly dif­fer, neither con­cern­ing elec­tron­ic­ally mon­itored early re­lease pre­par­a­tion (house ar­rest) nor elec­tron­ic­ally mon­itored work re­lease (see Meuer & Wößn­er).

In or­der to min­im­ize the in­flu­ence of pos­sible meth­od­o­lo­gic­al ar­ti­facts due to, e.g., the con­sid­er­able loss of sub­jects (see Schwedler & Wößn­er 2015), a second "twin" con­trol group was cre­ated by means of a matched-pair meth­od (n=45). This en­abled the ex­per­i­ment­al group to be com­pared with the ran­dom­ized con­trol group and the twin group. This second ana­lys­is con­firmed the res­ult of the ran­dom­ized study.