Self-service technologies within retail enable customers to scan, bag and pay for their items independent from staff involvement. The use of self-service, due to its nature of reducing social interaction between customers and staff, has been implicated in creating opportunities for thefts to occur. However, the perception of social presence, such as induced by surveillance, induces customers to show more prosocial behavior. As security personnel are at the forefront to deal with dishonest customers, we conducted semi-structured interviews with security guards in two major supermarkets in the UK to assess factors surrounding theft, with a view to identify operational or technological opportunities to address theft. Our findings show that the perceived motivational and situational factors contributing to theft are complex. We conclude that surveillance in its current form does not appear to provide a sufficient social presence to prevent potential theft at Self-Checkouts (SCO). Future research could focus on additional surveillance measures to induce social presence, such as technological implementations in the SCO itself.