Evelyn Stands Behind Jake (Dramatic Irony)
After learning a rude joke from his barber, Jake returns to his office excited to repeat the joke to his operatives. However, Jake is so pleased with himself that he dismisses the warnings of his employees and tells the joke while an elegant woman stands behind him, waiting to serve him with a lawsuit. In this instance of dramatic irony, the viewer and every character except Jake realize that something serious is about to happen while Jake remains oblivious.
Only When I Breathe (Verbal Irony)
After a thug with a knife slices Jake's nostril when he catches Jake investigating the Oak Pass Reservoir, Jake goes to Mr. Yelburton to question him about his involvement in the covert dumping of water. Seeing Jake's bandage, Yelburton says, "That must really smart." Jake replies, "Only when I breathe," prompting Yelburton to chuckle and repeat the line. In this instance of verbal irony, Jake makes it sound as though his wound is a minor inconvenience by including the word "only." However, he must breathe constantly to survive, so Jake is actually letting Yelburton know that his wound is always painful.
Katherine is Evelyn's Child and Sibling (Situational Irony)
At the film's climax, Jake confronts Evelyn about her attempts to deceive him about her involvement in Hollis's death. The distraught Evelyn confesses that Katherine is not Hollis's mistress, as Jake believed, but rather the child Evelyn gave birth to in Mexico after her own father impregnated her. In this instance of situational irony, Polanski subverts Jake's—and the viewer's—expectations with the revelation that Evelyn has been hiding the full truth of the case out of shame and a need to protect her daughter.
Jake Repeats His Past (Situational Irony)
After Jake and Evelyn have sex, she questions him about his past. Jake makes reference to a time when he was working for the DA in Chinatown: While trying to help a woman he'd developed feelings for, Jake unwittingly did something that put her in harm's way. The incident was significant enough that Jake's operative, Walsh, responds with alarm when Jake tells him to meet at Kahn's address in Chinatown; this reaction signals that whatever happened, Walsh understands Jake wouldn't want to return to Chinatown. In an instance of situational irony, Jake's attempt to protect Evelyn from harm and arrest precipitates a chain of events that results in her being shot in the head in front of her daughter, who is then claimed by the predatory Noah Cross. In the final line of the film, Walsh says, "Forget it, Jake. It's Chinatown." With this famous line, Walsh is letting Jake know there's nothing he can do to help at this point. Just as happened the last time he was in Chinatown, Jake's attempt to do good resulted in people being irreparably hurt.
