MEMPHIS (AP) — A federal judge has thrown out a lawsuit challenging the security of voting machines in Tennessee's largest county and calling for a switch to a handwritten ballot and a voter-verifiable paper trial.

U.S. District Judge Thomas Parker ruled Friday that the lawsuit filed by a group of Shelby County voters in October failed to show that any harm has come to the plaintiffs and that they have no standing to bring the suit.

Attorney Carol Chumney sued on claims that the outdated touchscreen voting machines used by Shelby County are insecure because they do not produce a voter-verifiable paper trail, and security checks and other safeguards are needed to protect the system from outside manipulation.

Cybersecurity experts have long complained that the nation's antiquated elections infrastructure is vulnerable to tampering.

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Jonathan Mattise contributed to this report from Nashville, Tennessee.