Jarvis Brown set out to disprove the old adage that a man who represents himself in court has a fool for a client. It didn’t go well.

Brown, 21, elected to serve as his own attorney in a one-day jury trial in Orleans Parish Criminal District Court on Tuesday. Police had alleged that he took part in three armed robberies in Lakeview on April 23, 2014, and he was convicted of all of them.

Authorities said Brown, who lives in New Orleans East, was in a group that robbed three people of their cellphones and wallets on Harrison Avenue, Porteous Street and Gen. Diaz Street within a span of 30 minutes.

Witnesses said the group drove a green Chevrolet truck with Texas license plates at high speed. According to a police report, officers tracked down the vehicle through the use of an app on one of the stolen phones. They found the green truck empty at Iberville and North Villere streets.

Undercover officers began watching the vehicle. When Brown; Gerald Williams, 23; and Jamal Bartley, 24, returned to the truck, they were arrested, the police report said.

Police said Brown had property from one of the robberies in his pocket. Two handguns were found inside the truck.

Williams pleaded guilty March 3 in exchange for a 15-year prison sentence.

Assistant District Attorney Sarah Dawkins opened the trial by outlining the evidence that detectives had gathered against Brown, including video that she said showed Brown using one victim’s debit card at a gas station.

“Jarvis Brown, along with two others, terrorized three people in the Lakeview neighborhood of New Orleans,” Dawkins said.

The state played 911 calls made immediately after the armed robberies, called all three victims to the stand and presented the testimony of Detective Stephen Kriebel.

Kriebel at one point narrated the video from the gas station showing someone using one victim’s debit card. “That gentleman right there is Mr. Jarvis Brown,” he said, pointing to the screen.

After several long seconds, Brown objected, saying, “The video speaks for itself.” Judge Karen Herman quickly sustained his objection.

Brown relied on the aid of a dictionary and Orleans Public Defenders staff attorney Sierra Thompson at the defense table. But he handled all questioning and arguments in the case himself.

Among the witnesses Brown called was Cindy Brown.

“How are you related to Mr. Brown?” the defendant asked.

“You’re my son,” she replied, adding that “you were at my house” at the time of the armed robbery spree.

Under cross-examination by Assistant District Attorney Taylor Anthony, the defendant’s mother faltered over just what her son was doing about 3:30 p.m. that day, at various points saying he was packing, going to church or working.

“I know he was helping me pack all that evening and all that night,” she finally said.

Brown also called on his grandmother to testify on his behalf, but he did not take the stand himself.

He claimed in his closing argument that he was misidentified by the victims.

“I was downtown after leaving my mother’s house to go downtown with some guys to smoke some pot,” he said.

“Mr. Brown never had any type of weapon in his possession when police arrested him,” he added.

Brown insisted that the evidence against him was weak.

“Clearly they’re lying about their case. They falsify their reports and do all kinds of corruption,” he said. “It’s basically hearsay. Their word against my word that I committed these robberies.”

Brown asked the jury “to open up in prayer” when it went to deliberate.

“I ask that y’all use your wisdom, your common sense and your third eye. Your sixth sense,” he said.

The jury reached its verdict — guilty as charged on three counts of armed robbery, marijuana possession and possession of a stolen credit or debit card — a little more than an hour later.

The judge set Brown’s sentencing for April 22. He faces a minimum 10-year prison term, with a maximum of 99 years for each armed robbery conviction.