In the movies and on TV, police work is often portrayed around the "stake-out" with "undercover cops". And, in the movies, car chases, foot chases over roof tops, and shootouts are the norm.
The Dallas Police Department calls its covert operations units Deployment Units. Each division has its own Deployment Unit, giving the city seven specially trained teams of officers as dedicated to combatting crime as are patrol officers.
Central's depolyment unit is comprised of eighteen officers, serving in two shifts. Each shift is comprised of eight deployment officers, supervised by a deployment sergeant. Each team reviews offenses from the previous day and compiles databases of offense data. The team looks for trends and formulates a plan for covert operations, with the goal of catching the bad guys in the act.
Deployment officers frequently work with patrol officers on operations. For safety (of suspects, the public and officers), patrol officers usually make contact with suspects when arrests are made, as patrol officers are uniformed and easily identifed as law enforcement officers. Traffic stops are always made by officers in marked patrol squad cars.
Deployment officers are the unsung heros of law enforcement. Officers' identies are protected, for officers' safety (the photograph above is not of Dallas officers, but of individuals from another part of the country), meaning they don't take public bows when they make arrests or stop crime trends.