Let's use math. Assume that the fugitive is fleeing with an average velocity v. While fleeing, he leaves behind a trail with a 'detectability rating' t(v) (t for trail). What this means is irrelevant, but t is an increasing function The pursuer is going to travel at a velocity w. While traveling at this speed, he can detect trails of at least strength d(w) (d for detect). d is also an increasing function So we have two conditions:
1) w>v is necessary for the pursuer to win
2) d(w)<t(v) is necessary for the pursuer to track his target
So the fugitive has the advantage as long as there exists v such that d(v)>t(v) and heuristically, the fugitive should escape nearly every time. Of course, in practice d is often much smaller than t (for example, if you have a helicopter and you're traveling behind the fugitive in a car, d is zero and will continue to be zero). So now it comes down to pure experimentation to determine the values of d and t