A Miami attorney's pants burst into flame on Wednesday afternoon as he was making closing arguments defending his client in an arson case.

Lawyer Stephen Gutierrez was arguing that the car of Claudy Charles, 48, burst into flame spontaneously in South Miami-Dade, rather than being intentionally set on fire, when witnesses saw smoke rising from Gutierrez's right trouser pocket.

Gutierrez rushed out of the courtroom, witnesses told the Miami Herald, but later returned uninjured with a burnt pocket, insisting that it wasn't a stunt to drive home his legal arguments. Gutierrez, 28, told the court that the battery in his e-cigarette had caught fire.

"It was surreal," a witness told the Miami Herald. Miami-Dade police are investigating and obtained an e-cigarette battery as evidence, according to The Herald.

Despite the interruption jurors chose to convict Charles of second-degree arson.

Judge Michael Hanzman, who was hearing the case at the Miami-Dade Criminal Court, could hold Gutierrez in contempt of court for the interruption.

E-cigarette batteries are known to spontaneously combust, and cases throughout the US and the world have caused severe injuries. Recently the devices, which vaporise nicotine, and are considered healthier than traditional cigarettes, have been banned from checked luggage on airplanes by the US Department of Transportation.