Her son was killed by North Korea's regime, and now she wants to prevent another American from being murdered by Kim Jong Un.

Cindy Warmbier, the mother of Otto Warmbier, the 22-year-old University of Virginia student who was falsely arrested, brutally tortured and sent home to Ohio to die by North Korea, brought a federal courtroom to tears as she pleaded for the life of former Marine Christopher Ahn.

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Christopher Ahn (U.S. Marine Corps)

"No one will stand up to North Korea. I'm left standing up to North Korea -- me. The government is pitiful. They won't stand up for Otto," she told the court.  

Warmbier, along with her husband Fred, appeared in a Los Angeles courtroom last week to ask the U.S. government to stop the extradition of Ahn, who served in Fallujah, Iraq, and was arrested when he returned from Spain in 2019.

He was part of an activist group that helps high-level North Korean diplomats and officials defect. Spanish authorities are asking the Biden administration to send Ahn back to face charges that he and his group broke into the North Korean embassy in Madrid. 

But Ahn and the group, Free Joseon, or Free North Korea, maintain that they were invited in as part of a planned mission to help Kim's ambassador defect, but the diplomat got cold feet at the last moment. 

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Cindy Warmbier and Ahn's supporters say he will be assassinated by the North Korean regime if he leaves U.S. custody. They fear he could also be kidnapped, transported to Pyongyang and subjected to a show trial before being executed in public. 

Experts say the Kim regime has a history of assassinating regime opponents across the globe.

The decision to grant Ahn’s extradition is now up to federal Magistrate Jean P. Rosenbluth.

"I know now they will kill Christopher Ahn. I don't know Christopher Ahn, but in my book … he's a hero," Warmbier said.

As she spoke at a podium protected by Plexiglas as a COVID-19 precaution, spectators could be heard weeping as she recalled her son and issued a heartfelt plea to the judge. 

"I need a strong woman who understands what I went through to stand up to North Korea. Otto was a beautiful boy. He was an incredible son. I had no idea what North Korea was about. I wish I had known," she said. "They took the most beautiful boy and destroyed him." 

She had sharp words for the Obama administration officials who kept reassuring the family that everything would be OK after Otto was arrested. Instead, he was returned by Kim’s regime  severely brain damaged, blind and unable to hear due to his torture. He died in a Cincinnati hospital six days after he arrived home.

"I begged the State Department. Please bring him home. He didn't do anything. 'Oh, he'll be OK. He'll be OK.' That's what they told me. That's what they'll say about Chris. He'll be OK. I'm sorry I'm so emotional. I'm sorry that I'm begging you, but the only thing I can do is stand up to North Korea and pray that more people will stand up to them. Please." 

Otto Warnbier was set to move to New York City to start an internship in the financial sector the summer he was nabbed. He had planned on moving to Manhattan after he graduated from college. 

"Cindy spoke with powerful, genuine, raw emotion," said Sung-Yoon Lee, a Tufts University professor and expert on Korea. He testified as a witness supporting Ahn's case to block extradition. 

"I heard and felt the cascade of audible crying and sniffling from the audience behind me," Lee told Fox News.

"As Cindy spoke of how North Korea had murdered her precious son Otto and how the U.S. government had utterly failed her, amid the audible chorus of crying, one could, paradoxically, hear a pin drop. It was a brief-but-prolonged scene in which a mother's anguished plea brought the judge, prosecution and defense all to a standstill as the sound of sighs and crying reverberated through the cavernous courtroom. An incredibly intense scene."

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Assistant U.S. Attorney John J. Lulejian argued that the Warmbier's plea should have no bearing on the extradition proceedings.

"While the United States empathizes with the Warmbiers and the tragic loss of their son, it must object to any attempt to expand these court proceedings – to which North Korea is not a party -- beyond their statutorily prescribed scope," he wrote in response.

He said it is up to the State Department to deny the extradition and argued that it should not be "denied on humanitarian grounds." Lulejian disputed the claims that Ahn would be in danger in Spain, and cited treaty obligations as the reason to uphold the extradition request.

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"Spain and all of our treaty partners must have confidence that the United States will adhere to the law when they submit a valid extradition request. The United States expects the same in the reciprocal context."

Rosenbluth is expected to issue her decision within a few weeks.

Fox News' Ben Evansky contributed to this report.