Language and communication are two different fields, but people have used them in various contexts. In courtroom, for example, a lawyer uses language to communicate the case at trial. Although many studies have addressed the language use in the courtroom communication, how language has power in the courtroom communication still has little attention. Therefore, this study aims to reveal how a lawyer's language becomes powerful in the courtroom communication. To meet this purpose, it discusses Johnnie L. Cochran's poetic language in his closing argument he delivered at the trial of O.J Simpson in 1995. In this discussion, the study focuses on three questions such as "which of Johnnie L. Cochran's sentences in his closing argument are considered as poetic language?", "how do the sentences of Johnnie L. Cochran become poetic?", and "why did Johnnie L. Cochran use the poetic language?". To answer these questions, the data were collected from the transcripts of Johnnie L. Cochran's closing argument obtained from http://simpson.walraven.org/sep27.html. In addition, the researcher analyzed the collected data using the analysis model of Miles and Huberman and thematic analysis. The results showed that with the use of repetition and rhyme in his closing argument, Johnnie Cochran succeeded in persuading the jury to acquit O.J Simpson of murder charges.