A U.S. Navy veteran and data scientist from Pennsylvania alleged this week that 47 USB cards used during the state’s Nov. 3 election have gone missing – and asserted that as many as 120,000 votes cast in the election should be called into question.

At a hearing in Gettysburg on Wednesday, poll watcher Gregory Stenstrom of Delaware County identified himself a former commanding officer in the Navy and a forensic computer scientist with expertise on security and fraud issues.

“I personally observed USB cards being uploaded to voting machines by the voting machine warehouse supervisor on multiple occasions,” Stenstrom testified. “This person is not being observed, he's not a part of the process that I can see, and he is walking in with baggies of USBs.”

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USB (Universal Serial Bus) cards are small, handheld devices that help people move data from one electronic device to another.

Stenstrom alleged the cards may have been used to add illegal votes to the state's vote count -- and claimed there was a lack of proper oversight on how state election workers handled ballots.

“In all cases the chain of custody was broken,” he said. “It was broken for the mail-in ballots, the drop-box ballots, the Election Day USB card flash drives. In all cases they didn't follow any of the procedures defined by the Board of Delaware County of Elections."

The witness also told lawmakers that law enforcement personnel failed to act after he reported the alleged mishandling of ballots.

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“I literally begged multiple law enforcement agencies to go get the forensic evidence from the computers. It's a simple process. It wouldn't have taken more than an hour to image all 5 machines. That was never done despite my objections and that was three weeks ago.”

The hearing was arranged by Pennsylvania state Republicans to address allegations of possible voter fraud following the election in a state where Democrat Joe Biden defeated President Trump by just over 80,000 votes, according to the Fox News Decision Desk.

Pennsylvania – which certified its election results Tuesday -- is one of several battleground states where the Trump 2020 Campaign has raised allegations of possible voter fraud. Pennsylvania was worth 20 electoral votes to the winner.

President Trump was initially scheduled to attend Wednesday’s hearing, which was convened by the Pennsylvania Senate Majority Policy Committee.

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The president later canceled his travel plans, opting instead to meet with his legal advisers in Washington. But Trump lawyer Rudy Giuliani appeared at the hearing.

However, the president’s legal fight in Pennsylvania continues. In a letter filed with the Third Circuit Court of Appeals on Wednesday, Trump 2020 Campaign attorney Marc Scaringi called for oral arguments as the campaign fights against a lower court’s dismissal of their case challenging Pennsylvania's certification of votes.