Final answer:
According to routine activities theory, a security guard serves as a Capable Guardian, deterring potential offenses by their presence and ability to intervene.
Step-by-step explanation:
According to routine activities theory, a security guard is an example of a Capable Guardian. This theory posits that for a crime to occur, three elements must be present: a motivated offender, a suitable target, and the absence of a capable guardian.
A capable guardian is someone who is present and able to prevent a crime from happening either by their mere presence or by intervening. A security guard, by surveilling and protecting a property or area, acts as a deterrence to potential offenders, thereby fulfilling the role of a capable guardian.