**3. Criminal career of sex offenders**

#### **3.1 Participation and frequency**

The dimension of participation refers to the proportion of a population who are active offenders at any given time, while frequency refers to the average annual rate at which this subgroup of active offenders commits crimes. In other words, participation refers to the prevalence of offending, while frequency refers to the incidence of crime [26]. Both dimensions are particularly difficult to research and estimate because of the underreporting of sexual offences and the so called "dark figures" of crime. Nevertheless, frequency has been of particular interest to the policymakers as it implicated that it is possible to identify high-frequency offenders and incapacitate them to maximise the incapacitation effect. However, it appears that the frequency of offending is very complex and that its value might fluctuate throughout a criminal career [27]. Another difficulty with the dimension of frequency is that it is challenging to estimate. For instance, one sex offender can offend against one victim over a, for example, 5-year period, multiple times, but official reports will note his offences as one offence.

The Cambridge study [28] found that the prevalence and frequency of sex offending in community samples is low and that that there is little evidence of recidivism or continuity. With respect to the prevalence and frequency of sex offending, conviction data indicated that whereas 41% of the males in the sample had been convicted by age 50, only 2.5% of the males had a conviction for a sex offence.

However, self-report and victimisation studies show a much higher number of individuals participating in sexual offending. For instance, The Bureau of Justice Statistics' (BJS) in the US conducts a National Crime Victimisation Survey (NCVS) [29] every year using a nationally representative sample of 240,000 interviews on criminal victimisation. Results for 2018 showed that the rate of rape or sexual assault victimisation increased 1.6 to 2.7 victimizations per 1000 individuals aged 12 or older in comparison to previous years. Even more concerning data emerged from two meta-analyses [30, 31] of 282 studies around the world on child sexual abuse. The analyses used self-report data and found that the prevalence of child sexual abuse ranges from 12.7–19.7% for girls and 7.6–7.9% for boys. Both analyses showed that the highest prevalence of sexual abuse of children is in Africa and the lowest prevalence rate in Europe.

It is important to point out that sexual offences are often generalised as heterosexual offence [32] and therefore, there is very little known about male victims [33].

#### *Identifying Criminal Career Patterns of Sex Offenders DOI: http://dx.doi.org/10.5772/intechopen.93972*

Recent figures indicate that around 12,000 males are victims of sexual assault or rape in the UK every year [34] and that nearly 1 in 4 men in the U.S. experienced some form of contact sexual violence in their lifetime. Among male victims of complete or attempted rape, about 71% experienced such victimisation before the age of 25 [35].

The frequency of offending varies significantly depending on the used method and between types of sex offenders. Sex offenders against women have, on average, 1.8 victims, whereas extra-familial child abusers have 3.4 victims on average [36]. Another study [37] suggests that sexual offenders with adult women victims had, on average, 2 official victims, but self-reported close to 12 victims. Similarly, sex offenders who offended against children had, on average, officially offended against 2 victims, but self-reported 7 victims.

Finally, investigations into the frequency of prolific, persistent sex offenders using several sources of information (i.e., self-reports, police investigations, victim statements) came up with three key conclusions on sex offending [38]. Firstly, about 11% of the sample committed over 300 sex crime events as opposed to about 40% who committed only one sex crime event. Secondly, some offenders take advantage of low-risk short-term opportunities with different victims, while others exploit a single offending opportunity by repeatedly offending against the same victim over a certain period of time. Thirdly, the findings revealed that the most prolific sex offenders were older, had a more conventional background characterised by a stable relationship with an adult partner, a job at the time of the offence (s), no drug issues, and no prior record for a sex crime.

#### **3.2 Seriousness**

The third dimension of the criminal career, seriousness, is in some ways, fundamental for criminal career research. Seriousness refers to the level of seriousness of the offences being committed by a given individual [3] and takes the modern approach to crime by focusing on determining a level of risk. Risk relates to the probability of criminal behaviour and is usually measured as low, moderate, or high [39, 40]. Offender risk is usually determined based on the possibility of reoffending or recidivism. It is important to define two categories here: chronic and recidivists [41]. The chronic type offenders are more at risk of persistent life-span criminal careers, which are costlier to society; over time they may have more victims (and financial loss for the victims) in addition to the costs associated with their arrest and incarceration. Recidivists are less persistent, as they have a lower incidence of reoffending. However, the categories do not differentiate on the severity of offences, only on offending timespan.

Offenders that maintain lengthier periods of offending tend to be generalists in their criminal behaviour [42, 43], their offences may be less severe than those that commit more severe types such as rape, sexual homicide, or child abuse. While there may be differences between types of reoffences (i.e. fraud and sex offences), society is risk-averse to more salient offences such as rape and child molestation [44, 45]. However, meta-analyses reports show that public fear of sexual offenders is often misplaced, and that offender's recidivism rates for sexual offences vary between 11,5% and 13,7% while general recidivism rate varies between 33,2% and 36,2% [46, 47].

Some authors argue that these four key dimensions of criminal career, and especially seriousness, made it possible for a variety of important theoretical opportunities to emerge along with research on criminal careers [48]. This segment of criminal careers has several parameters that are observed through the dimension of seriousness: the severity of the criminal offence, escalation, specialisation, and crime-type switching [49].

#### *3.2.1 The severity and escalation*

The severity of the offence refers to the tendency towards committing severe criminal offences during a criminal career while escalation refers to the tendency towards making initial minor offences towards the increasingly more severe offences [27]. Escalation reflects the concern that as the career develops, the offender engages in more serious offences. There are different causes for escalation, for example, experience, increasing boldness or a stressful experience [6, 27].

Escalation research emerged interesting findings such as that most sex offenders who perform masturbation in front of their victim do not switch to a different sexual act (for example intercourse) when they abuse their second victim [50]. This finding points out that sex offenders tend to specialise in a particular sexual act and that they are not likely to escalate their sexual offending from non-contact to contact offending, for instance.

Another interesting finding [51] suggested that victim resistance plays a significant role in whether or not offenders will de-escalate in the amount of physical force used between victims. If the first victim resisted the offender, he was more likely to de-escalate in the level of physical force used. However, if the second victim resisted, the offender was less likely to de-escalate, indicating that he is adopting more force to secure subsequent victims if there is resistance. Furthermore, sex offenders who consume drugs in the hours before the first crime are more likely to de-escalate in the level of physical force used than be stable.

Crucial to determining behaviour consistency is the way an offender sources his victims. The "hunting" process is an essential stage of the sexual assault and offenders who find their victims through their relationships, or their occupation will often repeat their behaviour in their future crime. In contrast, offenders who find their victims more spontaneously are less likely to repeat this "hunting" method [52].

#### *3.2.2 Specialisation and crime-type switching*

Specialisation is an aspect of criminal careers and is defined as likely repetitions of the same type of criminal offence [23] while versatility reflects a tendency to commit a broad array of offences without concentrating on a specific behaviour. Researchers use a "crime-switch" matrix, a matrix of crime types reflecting the probability that an offender who has previously committed one crime type will next commit a different type [27]. Research showed that there is a relationship between higher frequency of offending and versatility, but also that offenders who start offending at an early age tend to be involved in a diverse array of offences [6]. Most criminal careers are diverse, but there is some evidence of specialisation [21].

Sex offenders in specific show little empirical evidence of specialisation, but they are characterised by persistent criminal activity and tend to show criminal diversity in non-sexual crime types [53]. It was also found [54–56] that there are substantial differences between sex offenders regarding victim type. Sexual offenders against adults have more versatile criminal records [54–56], are more violent and have a higher frequency in offending [56] than abusers of children. The other group tends to be more specialised, have a higher frequency of sexual crimes, but also tend to be criminally versatile [45–56]. Extrafamilial child molesters are consistently found to specialise more in sexual offences [54, 55]. Overall, neither child abusers nor sex offenders against adult women have a specific type of victim and that the majority of both types typically commit more non-sexual offences than sexual [56].

#### **3.3 Career length**

The last dimension of criminal career research is the length; that is the time that an individual is actively offending. Research on the dimension of length attracted the attention of the scholarly community from the very beginning of criminal career research. It incorporates three head characteristics of criminal careers: beginning ("onset" or "initiation"), duration and end ("desistance" or "termination") [2, 10].

The relationship between age and crime is of an asymmetrical bell shape (most commonly known as the "age-crime curve"), showing that the prevalence of offending tends to increase from late childhood, peaks in the teenage years (around ages 15–19), and then declines from the early 20s, often with a long tail [22]. Most offenders desist during late adolescence and early adulthood, irrespective of the age of onset [22], but an early age of onset appears to be connected to a relatively long criminal career [6, 50]. Research on recidivism shows that sexual offending decreases with age, as well as general offending, and the recidivism of sexual offenders that offend against adult decreases from early adulthood [57, 58]. However, unlike the general offender, sexual offenders usually start committing offences either in adolescence or in mid to late 30 [2, 59].

Some of the possible explanations of why sex offenders appear to be older when they start offending include that there is a high rate of unreported sex offences because the victims are less likely to report sexual offences than non-sexual offences and because there is a disbalance between official statistics and self-report. A gap between the age of onset in the official statistics and self-report is seven years [2]. Moreover, nearly 20% of sexual offenders are at the end of their criminal career, or their career has already desisted when they are convicted of their first sexual offence [2].

Alternatively, some authors [60] suggest that the discrepancy that goes against the logic of the life-course explanation of desistance could be explained by increased average ages of marriage and parenthood. In specific, the peak in sexual offending seems to occur at a time when adolescents already transitioned into adulthood which could mean that sex offenders do not transition into adulthood at the same pace as non-sexual offenders, or that these transitions do not affect recidivism in the same way as they do non-sexual offenders. Besides the transition into adulthood, several other reasons could influence individuals to start with sexual offending. For example, loneliness is commonly reported among sex offenders, that the transitions that influence common crime do not affect sexual offending (or affect it to a lesser extent), a cost-benefit analysis that makes sex offenders less likely to accept the cost of being labelled as a sex offender, conflicting interpersonal relationships, and maturation factors [60].

The above-described factors could affect the length of a criminal career, but the most significant variable affecting the length of a criminal career is the age of the first conviction. The likelihood of termination of offending is noticeably different as the age of the first conviction rises, and more severe offenders cease to offend after the first conviction only in fewer cases [61].
