Why bother with actual torture when psychological tricks work better?
Frank Sinartra's greatest hits, plus some light folk and maybe a spot of Enya to be going on with together with nice, comfortable seats and a fairly high ambient light level and maybe even a coffee shop. That will make that particular shopping mall a hit with the older generation, and a place where pensioners love to gather, read the paper, have a chat and so on is a place like one of the circles of hell to a teenager.
Do that and the teenagers will turn up, shop and scarper as fast as their legs can carry them, whilst the oldsters (who are mostly unthreatening and non-criminal) will linger and spend money.
Biting the hand that feeds IT
