Bad Lieutenant was a 1992 film directed by Abel Ferrara that starred Harvey Keitel as the titular member of a police force. Let it be known that while similar in theme and name, 2009's Bad Lieutenant: Port of Call New Orleans by Werner Herzog has absolutely nothing to do with the original. It's by no means a continuation of the storyline, or even involved in any way with Ferrera's production, it's just merely a coincidence apparently. New Orleans is its own film and stands on its own two feet, and that's thanks largely to the stellar performance by Nicolas Cage.
Bad Lieutenant: Port of Call New Orleans begins shortly after Hurricane Katrina devastated New Orleans. Sergeant Terrence McDonagh (Cage) and Stevie Pruit (Val Kilmer) are pawing through the records of a flooded and deserted prison when they discover a prisoner up to his neck in water. Time's running out for the prisoner as McDonagh and Pruit poke some fun at him for the situation he's in. Eventually McDonagh's conscience gets the better of him and he jumps into the water to rescue the convict. This is the singular event that sends his life in a downward spiral due to a severe back injury he sustains from the jump.
For his bravery in the line of duty McDonagh is promoted to Lieutenant. Though crippled, he's more than able to do the job, but he needs something to take the edge off so he begins with prescription painkillers. It's not long before one drug leads to another and eventually McDonagh is hitting whatever illegal drugs come his way. Coke, heroin, and pot all make their way into his hands through the use of intimidation on the street and the property department at his station. In this regard Port of Call New Orleans is a fascinating deconstruction of the man as he just keeps going from bad to worse.
Drugs aside, McDonagh is still able to perform his job quite well. He's been placed in charge of the investigation of a family's murder and that serves as his driving force. He's willing to do whatever it takes to function with the pain, and whatever it takes to see that the killer is brought to justice. It's not long until the investigative path leads him to the area's largest drug dealer and I think you can imagine what happens here considering McDonagh's addictions.