A tracker dog

benefit (be or provide a benefit to)

useless, deadhead, good-for-nothing, a piece of shit / (politics) lame duck

flee, escape

flight, getaway, escape

to chase, to pursue at speed / to track, to follow the traces of something

chase, pursuit / tracking, following

dog; canine / one who is loyal (like a dog) / a spy

perpetrators of a crime / some types of crime

crime, offense / criminal, culprit, offender / disciplined monk committing such offense