A grand jury on Tuesday indicted the St. Louis, Mo., couple who displayed guns while hundreds of racial injustice protesters marched on their private street in June.

Al Watkins, an attorney for the couple, confirmed to The Associated Press indictments against Mark McCloskey, 63, and his wife, Patricia McCloskey, 61. A spokesperson for Circuit Attorney Kim Gardner declined comment.

The McCloskeys, who are both attorneys, have become folk heroes among some conservatives. They argue that they were simply exercising their Second Amendment right to bear arms, and were protected by Missouri's castle doctrine law that allows the use of deadly force against intruders.

The case has caught the attention of U.S. President Donald Trump, and Republican Missouri Gov. Mike Parson has said he will pardon the couple if they are convicted.

The McCloskeys also were featured speakers on the first night of the Republican National Convention. They've accused the "leftist" Democratic St. Louis leadership of causing their current plight.

But Gardner, a Democrat, charged the couple with felony unlawful use of a weapon. She said the display of guns risked bloodshed at what she called an otherwise peaceful protest.

Watkins said that in addition to the weapons charge, the grand jury indictment includes a tampering with evidence charge. It wasn't clear what led to that additional count, he said.

The McCloskeys contend the protest was hardly peaceful. They say protesters came onto the private street after knocking over an iron gate and ignoring a "No Trespassing sign," and said they felt threatened.

Watkins said accusations against the McCloskeys are "effectively demonstrating the highest degree of ineptitude and inappropriate behaviour" from Gardner's office.

The incident happened during a June 28 protest — one of hundreds held nationwide in the aftermath of the death of George Floyd at the hands of Minneapolis police — as demonstrators were walking toward the home of St. Louis Mayor Lyda Krewson a few blocks away.

The protesters suddenly decided to veer onto the McCloskeys' street, prompting the confrontation that was caught on cellphone video. It showed Mark McCloskey in front of the $1.15 million US home armed with an AR-15 rifle and Patricia McCloskey armed with a semi-automatic handgun.

A police probable cause statement said protesters feared "being injured due to Patricia McCloskey's finger being on the trigger, coupled with her excited demeanour."

Nine people involved in the protest were charged with misdemeanour trespassing, but the city counsellor's office later dropped the charges. The city counsellor's office handles lesser crimes and is not affiliated with the circuit attorney's office.

Mark McCloskey, after a brief court hearing last week, expressed anger that he and his wife faced criminal charges while those who trespassed onto his property did not.

"Every single human being that was in front of my house was a criminal trespasser," McCloskey said on Oct. 6. "They broke down our gate. They trespassed on our property. Not a single one of those people is now charged with anything. We're charged with felonies that could cost us four years of our lives and our law licences."