The title of this film announces its trajectory, although it seems, in its content, to be more or less a story of cops that go bad in trying to do good. This story-arch, namely up and then down--although in this film, really, things just get bad and then get worse--requires that the film absorb its actors within a grand scope in which they are merely events that occur. But the real subject of the film would be the city.
There are few directors that are capable of making films about a city. Among them, off the top of my head, I would include Michael Mann (Mann made one of Peterson's first films, "Manhunter" which constituted the first installment of the laborious Hannibal Lector saga, long before Jonathan Demme got ahold of it in the "Silence of the Lambs") and Federico Fellini ("Fellini Roma"; "La Dolce Vita"; etc.). In this register, Mann has undoubtedly been more successful, although to do this issue justice one must acknowledge the different meanings of the city between Mann and Fellini. In Fellini, the city is the people and the culture, whereas in Mann the city is the image. For Americans, only the latter, it seems to me, is really meaningful, although I think that "To Live and Die in L.A." contributes to Fellini's city-perception.
To summarize, William Peterson (now best known for CSI, unfortunately) plays Richard Chance, a secret service agent that is pursuing the counterfeiter Rick Masters, played by a young, luminous Willem Dafoe. Chance and Dafoe typify, in almost the same way, the image of L.A. Chance, in addition to his profession, is a base jumper. This we discover at the beginning, when we see him perched on the edge of a bridge that, a moment later, he jumps from. Of course, the images intend our confusion, thinking Chance suicidal. Then we see the cord attached to Chance's leg. His surname, is, I guess, a blatant indication of the same. The only meaningful life involves extreme risk.
Masters, by contrast, is an artist who burns his paintings, and then counterfeits cash. He has a girlfriend who is a dancer, that at first, appears a man whom Masters passionately kisses (it seems pertinent to point out that the director, William Friedkin, also directed "Cruising"). He has no qualms about killing that interfere in his business or try to cheat him. He seems unassailably cool and calm and lives a life of narcissistic contemplation (several scenes of him with girlfriend, in flagrante delicto, videotaping himself).
And the moral of this story is (pace Lewis Carroll) that in L.A. people drive fast, are all felons or will be soon, put no real value on human life, are themselves merely parts of concrete and ash and powder, momentarily in flight.
(Oh yeah: they also listen to ass music and have one of the most incredible chase sequences ever)