Trailing dogs follow the odor a person has left as they travel, sort of like following bread crumbs. Trailing dogs my work directly in the footpath of the person, or even yards away, depending on wind and environmental conditions. Trailing dogs are best deployed prior to heavy contamination of the scene, and as a first response, preferably within the first 48 hours of operation. A PLS or LKP is needed.
CBSD trailing dogs train routinely in both urban and wilderness environments, often with high contamination and trails aged from 15 minutes to multiple days old.