Corruption
One of the main themes of the film is the corruption that lies within the power structures of America. The drug cartel is manipulating the LAPD, and private corporations. And, we see Nazis seeking to corrupt real estate on the Las Vegas strip as well as in Los Angeles in order to gain control of highly prized land. These combined with the personal corruptions of the characters, including Bigfoot's willingness to pin murder and stolen heroin on Doc, lead to a volatile mixture of conflict throughout the story.
Betrayal
Shasta Fay comes to Doc in order to get help. She's in a tight situation and calls on her former boyfriend, and private investigator in order to get her out of a jam. However, what appears as a woman in desperate needs turns out to be someone who is willing to manipulate someone who loves her in order to protect herself, regardless of the consequences, including the potential for death, for Doc.
Realty and Hallucination
Doc is a man who is almost always high. It is 1970 Los Angeles, and he enjoys the constant intake of various drugs. What this causes, though, is his need to distinguish reality from hallucination and leads him into dangerous situations, and in some cases protects him (his instinct to look in his trunk for the heroin). Sortilege represents this uncertainty of being in reality or hallucination as she is seen with Doc, talking and conferring with him, but in the same breath disappears from his side.