ATLANTA (AP) — Election integrity activists want a federal judge to order Georgia to stop using its current election system, saying it’s vulnerable to attack and has operational issues that could cost voters their right to cast a vote and have it accurately counted.

During a trial set to start Tuesday, activists plan to argue that the Dominion Voting Systems touchscreen voting machines are so flawed they are unconstitutional. Election officials insist the system is secure and reliable and say it is up to the state to decide how it conducts elections.

Georgia has become a pivotal electoral battleground in recent years with national attention focused on its elections. The election system used statewide by nearly all in-person voters includes touchscreen voting machines that print ballots with a human-readable summary of voters’ selections and a QR code that a scanner reads to count the votes.

The activists say the state should switch to hand-marked paper ballots tallied by scanners and also needs much more robust post-election audits than are currently in place. U.S. District Judge Amy Totenberg, who’s overseeing the long-running case, said in an October order that she cannot order the state to use hand-marked paper ballots. But activists say prohibiting the use of the touchscreen machines would effectively force the use of hand-marked paper ballots because that’s the emergency backup provided for in state law.

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Wild conspiracy theories about Dominion voting machines proliferated in the wake of the 2020 election, spread by allies of former President Donald Trump who said they were used to steal the election from him. The election equipment company has fought back aggressively with litigation, notably reaching a $787 million settlement with Fox News in April.

The trial set to begin Tuesday stems from a lawsuit that long predates those claims. It was originally filed in 2017 by several individual voters and the Coalition for Good Governance, which advocates for election integrity, and targeted the outdated, paperless voting system used at the time.

Totenberg in August 2019 prohibited the state from using the antiquated machines beyond that year. The state had agreed to purchase new voting machines from Dominion a few weeks earlier and scrambled to deploy them ahead of the 2020 election cycle. Before the machines were distributed statewide, the activists amended their lawsuit to take aim at the new system.

They argue the system has serious security vulnerabilities that could be exploited without detection and that the state has done little to address those problems. Additionally, voters cannot be sure their votes are accurately recorded because they cannot read the QR code, they say. And the voting machines’ large, upright screens make it easy to see a voter’s selections, violating the right to ballot secrecy, they say.

Lawyers for Secretary of State Brad Raffensperger wrote in a recent court filing that he “vigorously disputes” the activists’ claims and “strongly believes” their case is “legally and factually meritless.”

Experts engaged by the activists have said they’ve seen no evidence that any vulnerabilities have been exploited to change the outcome of an election, but they say the concerns need to be addressed immediately to protect future elections.

One of them, University of Michigan computer scientist J. Alex Halderman, examined a machine from Georgia and wrote a lengthy report detailing vulnerabilities that he said bad actors could use to attack the system. The U.S. Cybersecurity and Infrastructure Security Agency, or CISA, in June 2022 released an advisory based on Halderman’s findings that urged jurisdictions that use the machines to quickly mitigate the vulnerabilities.

During a hearing in May, a lawyer for the state told the judge physical security elements recommended by CISA were “largely in place.” But the secretary of state’s office has said a software update from Dominion is too cumbersome to install before the 2024 elections.

The fact that the voting system software and data was uploaded to a server and shared with an unknown number of people after unauthorized people accessed election equipment in January 2021 makes it even easier to plan an attack on the system, Halderman has said. That breach at the elections office in rural Coffee County was uncovered and exposed by the plaintiffs in the lawsuit.

A sprawling Fulton County racketeering indictment against Trump and 18 others included charges against four people related to Coffee County. Two of them, including Trump-allied lawyer Sidney Powell, have pleaded guilty after reaching deals with prosecutors.

In several rulings during the litigation, Totenberg has made clear that she has concerns about the voting system. But she wrote in October that the activists “carry a heavy burden to establish a constitutional violation” connected to the voting system or its implementation.

David Cross, a lawyer for some of the individual voters, said the judge has only seen a sliver of their evidence so far. He said he believes she’ll find in their favor, but he doesn’t expect to see any changes before Georgia’s presidential primary in March. He said changes might be possible before the general election in November if Totenberg rules quickly.

“We’re hopeful but we recognize it’s an uphill fight for 2024, just on the timing,” he said, acknowledging the likelihood that the state would appeal any ruling in the activists’ favor.

Marilyn Marks, executive director of the Coalition for Good Governance, was similarly optimistic ahead of trial: “We have the facts and the science and the law on our side, and really the state has no defense.”

A representative for Raffensperger didn’t respond to multiple requests to interview someone in his office ahead of the trial.

The activists had planned to call the secretary of state to testify. They wanted to ask why he chose a voting system that uses QR codes that aren’t readable by voters. They also believe his office has failed to investigate or to implement proper safeguards after the Coffee County breach and wanted to ask him about it under oath.

The judge ordered him to appear over the objections of his lawyers. But the 11th U.S. Circuit Court of Appeals on Friday ruled he doesn’t have to testify, citing his status as as top official and saying the plaintiffs didn’t show his testimony was necessary.

“This trial bears heavily on the public interest, and voters deserve to hear from Secretary Raffensperger in the trial. It’s a travesty that they won’t,” Cross said. “And it’s unfair to our clients who need answers to questions at trial that only he can provide.”