A former Dallas police detective -- paralyzed from an on-the-job shooting -- is still helping catch the bad guys.  Police credit David Rodriguez for helping catch an armed robber after Rodriguez witnessed a fast-food restaurant stick-up in Oak Cliff on Monday.  Rodriguez called 911 and directed police to where the robbery was going down.  As the guy got away, Rodriguez followed him in his specially-equipped pick-up.  The robber saw he was being followed -- and pulled his gun and pointed it at Rodriguez.  But the retired officer kept him in sight -- and guided officers to where he was hiding under a dumpster.  In 1994, Rodriguez was paralyzed from the chest down.  He was shot in the neck during a raid to serve warrants in northwest Dallas.