Its a mechanical problem. If someone is on the move, there is no way to catch him.
-Unless he lags.
-Gets stuck on a wall.
-Runs out of moves.
If you open with murder (engage with murder player), they can still just flee and start moving fast.
There are no chasing scripts for FL. (Unless ranger track skill allows you one.)
To catch people you need to:
Lag them so they dont escape (Bash/Bodyslam/Trip)
Blind them, so they run into walls (Dirt Kick, narrow twisted roads)
Drain their moves to Zero. (Shaman, Necromancers..., hard)
Getting the kill is the hardest thing to do. Many times you beat them just to have them slip throuhgh your fingers.
Basic killing for a warrior is droping their HP low enuff.
If its a not a mage/cleric class Enlarge and Bash to keep them in battle.
If its a mage keep them dirted, and wait for them to flee and then chase with Charge. So that you burst a huge amount of damage. If that does not kill them lead with murder.
Mages will most time recall and get to their temple. Fight near their temples. Or curse them before (hard to a warrior).