Criminologists Cohen and Felson (1979) proposed a “basic chemistry of a crime” (figure 1), not just to do with sexual abuse. For any crime to occur, three necessary elements must converge: a likely offender; a suitable target; and the absence of a capable guardian. They state that many people have the potential to be offenders but do not actually offend. Such individuals need the opportunity to encounter a suitable target, in the absence of a capable guardian, in order to convert their criminal potential into criminal actions. A crucial element in the commission of a crime is the presence or otherwise of another person. Most (potential) crime is prevented not by police but by ordinary citizens going about their day-to-day “routine activities”. People routinely look out for their own children as well as those of others; just as they lock their cars, bikes and houses. Such actions make a considerable difference to rates of all crimes, including sexual abuse.

Eck (2003) further developed thinking about third parties by proposing three types of “crime controllers”. He used the term “guardian” to refer to persons with the responsibility, interest and capacity to protect the potential victim. So, we might think of a parent, a sibling, a teacher or a peer who protect the child. Eck’s second type of crime controller is a “handler”, who can exert a positive influence over the potential offender, such as parents, teachers, friends and work colleagues. The third of Eck’s crime controllers are “place managers”, responsible for supervising and maintaining good conduct in specific places such as schools, residential homes, leisure centres, parks and so forth. Place managers can include teachers, security guards, park wardens and residential staff.

We must also consider criminological thinking about developmental crime prevention. Sex offending has been linked to individual impulsivity, poor problem-solving and family adversity - including domestic violence and parental substance misuse (Salter et al, 2003; Skuse et al, 1998). For some boys, their experience of sexual abuse in childhood is coming to be recognised as a risk factor for sexual offending (Ogloff et al 2012). Early interventions to reduce the impact of these childhood experiences might reduce the risk of future sexual offending.

In 2008, Smallbone, Wortley and Marshall published their important work, “Preventing Child Sexual Abuse”, which includes a comprehensive child sexual abuse prevention framework.(Smallbone et al 2008). Their public health model distinguishes between primary (or universal), secondary (or selected), and tertiary (or indicated) prevention. Whilst there is not universal agreement about the precise distinctions between primary, secondary and tertiary prevention when applied to crime, the crucial insight is the possibility that interventions may be directed to preventing sexual violence before it would otherwise first occur (primary or secondary prevention); as well as after its occurrence, to prevent further offending and victimisation (tertiary prevention). 
The comprehensive prevention framework (see figure 2 below) incorporates the criminological thinking referred to above and invites us to consider targets for interventions that:-

• prevent offending or re-offending by offenders (who, before they offend, are termed potential offenders);
• prevent victimisation or re-victimisation of children 
• prevent an offence or further offence within a specific family or community; and 
• prevent an incident or recurrence of child sexual abuse in a specific situation or place
   

This work gives us the basis for discussing and agreeing the most hopeful components of a strategy for the prevention of child sexual abuse. But to be most useful, it needs to be applied by those with a good understanding of the problems of abuse in their area, city or country - the particular nature of abuse varies from place to place, and a prevention strategy needs to respond to the circumstances of the place where it is to be implemented.