Why fixed-timing patrols fail
A predictable patrol is a schedule for the intruder. Vary start times, direction and pace. If you always start clockwise at :00, everyone who watches you knows it.
Guard-tour technology
RFID or QR checkpoints prove attendance and generate defensible logs. Log exceptions (missed checkpoint, delay, incident) — that is what an audit values.
Sensory patrol
Smell (gas, burning, cannabis, damp), hearing (dripping water, unusual mechanical noise), temperature (unexpected warmth or cold in enclosed spaces), light (unexpected on/off). Half the incidents you'll ever detect will be through a non-visual sense.