The legal definition of what constitutes child pornography, as well as the interpretation and enforcement of statutory provisions relating to child pornography, vary considerably from country to country. Not surprisingly, the definitions of child pornography to be found in the relevant research literature are equally heterogeneous [1–3]. The definitions differ regarding the age boundary of consenting adult vs. child and in respect to how explicit the sexual depiction of the material must be in order to be considered "illegal pornography". Furthermore, some criminal codes penalize only the production and distribution of illegal pornography, while others criminalize the possession as well.

In April 2002, a new article was introduced into Swiss penal law stating that the possession of pornographic material depicting sexual acts with children, excrement, animals, as well as violent sexual intercourse, is illegal (Art.197 Swiss Penal Code). Accordingly, the production, import, storage, marketing, making available, and presentation of illegal pornography is a punishable offense. Before April 2002, only the trade and production of child pornography was against the law, not its possession. Swiss penal law neither specifies the age which discriminates children from adults, nor does it specifically state the exact characteristics of pornography. However, judicial practice defines children younger than 16 as juveniles, which is also the appointed age of consent [4, 5].

The high accessibility of the Internet has changed the consumption of child pornography. According to Cooper, Delmonico and Berg [6], three attributes of the Internet, called the "Triple A Engine", facilitate the consumption of child pornography: Accessibility (millions of websites are accessible 24 hours a day, 7 days a week), affordability (acquiring the material does not demand substantial financial resources), and anonymity (no personal contact with others is needed to consume child pornography). Quayle, Vaughan, and Taylor [7] also underline the importance of the ostensible anonymity of the Internet for the consumption of Internet child pornography, as it does not require contacting a dealer and the material can easily be acquired at home. Furthermore, virtual pornographic material can be stored easily and no strenuous effort is needed to keep the illegal material hidden [8].

One of the most consistent findings when trying to characterize the "typical" user of child pornography is – not surprisingly – that there are only male consumers [1, 9–16]. According to Quayle, Erooga, Wright, Taylor and Harbinson [2], it is safe to assume that female child pornography consumers are non-existent. Furthermore, there is evidence that consumers of child pornography have a relatively high educational background. According to Wolak, Finkelhor and Mitchell [16], 38% out of 1,713 convicted consumers of child pornography in the U.S. had a high-school diploma, 21% went to college at some point, 16% held a college diploma, and 4% finished their education at a doctoral level. This finding was corroborated by Riegel [13], who found that 77% of his sample of alleged pornography consumers consisted of college graduates. In the Swiss study of Frei, Erenay, Dittman and Graf [1], one out of three child pornography users reported working in an executive position or holding an academic degree. Burke, Sowerbutts, Blundell and Sherry [4], as well as O'Brien and Webster [17], found higher scores of intelligence, a better educational background, as well as a higher rate of employment for Internet child pornography consumers than for hands-on sex offenders.

When investigating the prevalence of Internet child pornography consumption, an important practical question is whether consumers of child pornography pose a risk for hands-on sex offenses. Empirical studies use different study designs and samples for answering this question. However, there are three main approaches to be found in the relevant research literature.

Firstly, there are studies that examine the role of child pornography consumption on offending in samples of hands-on sex offenders [10, 15]. Following such an approach, Kingston, Fedoroff, Firestone, Curry and Bradford [10] examined convicted hands-on sex offenders and found that the consumption of illegal pornography was a relevant risk factor, namely that those offenders who had consumed illegal pornography were more likely to re-offend – irrespective of their risk-level of recidivism. Howitt [9] investigated convicted hands-on sex offenders, who reported that the source of sexual stimuli did not stem solely from child pornographic material, but also from the cognitive manipulation of legal adult pornography or from seeing arousing images in newspapers and magazines (usually not involving nudity). Unlike Kingston et al. [10], Howitt [9] concluded that it is not possible to establish an association between hands-on sex offenses and the consumption of child pornographic material. Since Kingston et al. [10] and Howitt [9] investigated samples containing only hands-on offenders, it is evident, that the conclusions of these authors cannot be generalized to hands-off offenders.

Secondly, there are studies that examine the prevalence of prior convictions for hands-on sex offenses in populations of child pornography consumers [1, 14, 15].

Webb, Craissati and Keen [15] compared 90 child pornography consumers with 120 offenders convicted of hands-on sex offenses. The number of offenders with prior convictions for sexual offenses was higher in the group of hands-on sex offenders than in the group of child pornography users. In an investigation by Frei, Erenay, Dittmann and Graf [1], none of the child pornography consumers had a criminal record.

This approach allows an initial conclusion to be drawn regarding the prevalence of hands-on sex offenses for child pornography consumers. However, due to the limitations of retrospective designs, it cannot answer the question of whether child pornography consumption represents a risk factor for committing hands-on sex offenses in the future.

Thirdly, research designs following up on a sample of offenders convicted of child pornography consumption would appear to be the best approach [14]. So far, there is only one study that has analyzed the association between child pornography consumption and the subsequent perpetration of hands-on sex offenses [14]. In their sample of convicted child pornography consumers, Seto and Eke [14] found a recidivism rate of 1.3% for hands-on sex offenses and 5.3% for hands-off sex offenses in a follow-up time of two and a half years. In this study, 24% of the study sample had been convicted for a hands-on sex offense against a minor. An Internet based survey by Riegel [13] found results pointing in the same direction as Seto and Eke's: Participants identifying themselves as "Boy-Attracted Pedosexual Males (BPM)" were asked whether the consumption of child pornographic material increased the desire to commit sexual acts with minors, 84.5% of the survey sample replied „rarely" or „never". The author interpreted this finding as an indication that the consumption of child pornography alone is not a sufficient risk factor for committing a hands-on sex offense.

Altogether, the empirical literature does not put forward any evidence that the consumers of child pornography pose a considerably increased risk for perpetrating hand-on sex offenses. Instead, the current research literature supports the assumption that the consumers of child pornography form a distinct group of sex offenders. Though some consumers do commit hands-on sex offenses as well – the majority of child pornography users do not. Previous hands-on sex offenses are a relevant risk factor for future hands-on sex offenses among child pornography users, just as they are among sex offenders in general. The consumption of child pornographic material alone does not seem to predict hands-on sex offenses.

The aim of this study was to analyze the characteristics of a sample of child pornography users and the proportion of those who subsequently re-offended with hands-on and hands-off sex offenses.

For the present study, the criminal records of all men charged with child pornography, as a result of the police operation "Genesis", were analyzed. This study is one of the few scientific reports covering a six year follow-up period of a sample of subjects charged with the consumption of child pornographic material.

Descriptive analyses suggest that child pornography users are less likely to be married: While only one out of three subjects was married at the time of the police operations, the census data of the Canton of Zurich reported that 45% of the Swiss male population living in the Canton of Zurich was married. Moreover, the foreign nationals (6%) in the present study were underrepresented in comparison to the 31% of foreign male residents in the Canton of Zurich [19]. This finding is remarkable seeing as this underrepresentation cannot be found for hands-on sex offenses [20]. As in other studies [4, 13, 16, 17], the finding that child pornography consumers are well educated was replicated in the present study: Only 5% of the investigated sample held an unqualified job position – a figure that is rather low compared to the 16% of unskilled workers in the permanent living population of the Canton of Zurich [21].

In summary, our results suggest that users of child pornography are probably well integrated in Swiss society, as the majority of subjects held a job requiring extensive training and were Swiss nationals.

The question of whether consumers of child pornography pose a risk for hands-on sex offenses has not yet been answered. In their sample of child pornography users, Seto und Eke [14] found that 24% of the study sample had a criminal record for a hands-on sex offense against a minor and 15% had a prior conviction for the possession of child pornography. Other studies however, have found low rates of previous convictions for hands-on sex offenses among child pornography consumers [4, 15].

In our study, we were able to replicate the finding that the majority of child pornography consumers do not have a criminal record for a violent and/or sex offense. Before the police operation, 3.5% of the study sample had prior convictions for a hands-off sex offense and 1% (n = 2) for hands-on sex offenses involving child sexual abuse. We cannot explain the large difference of prior conviction rates in our sample compared to Seto and Eke [14] – further research would be necessary to find out if they differ significantly in regard to socio-economic, educational and/or other variables.

Studies investigating hands-on sex offender populations support the assumption that the consumption of illegal pornography is a relevant risk factor for recidivism [10]. In contrast, Seto and Eke [14] found low recidivism rates for both hands-on (1.3%) and hands-off (5.3%) sex offenses in a follow-up time of two and a half years for their sample of child pornography consumers.

Similar to Seto and Eke [14], we found low rates of recidivism among our sample. When applying the broader definition of recidivism by taking investigations and charges into account, the recidivism rates were 0.8% for hands-on and 3.9% for hands-off sex offenses. These recidivism rates after a follow-up time of six years indicate that the risk of re-offending for child pornography consumers is quite low.

Among the subjects of the present study, only 1% were known to have committed a past hands-on sex offense, and only 1% were charged with a subsequent hands-on sex offense in the 6 year follow-up. The consumption of child pornography alone does not seem to represent a risk factor for committing hands-on sex offenses in the present sample – at least not in those subjects without prior convictions for hands-on sex offenses.