Who is Maryellen Noreika, the Trump-appointed judge presiding over Hunter Biden case?

President Joe Biden's son Hunter Biden was in federal court on Wednesday as a judge weighed whether to reject or accept the terms of a plea deal he negotiated last month with federal prosecutors.

Judge Maryellen Noreika, who is presiding over the case in Delaware federal court, deferred the plea deal after an hourslong, contentious hearing. She expressed concerns with the structure of the agreement and requested additional briefings from both parties in the coming weeks before determining the next steps.

"I'm not going to say I'm going to accept the agreement, I'm not going to say I'll deny it," she said, acknowledging that her probing threw "a little bit of a curveball" into the proceeding.

Noreika was confirmed as a district judge in the District of Delaware in August 2018, following a nomination by former President Donald Trump in December 2017 to fill a seat vacated by Gregory Sleet upon his pending retirement.

Noreika worked in private practice from 1993 to 2018 prior to becoming a federal judge, according to her federal biography.

She graduated from the University of Pittsburgh School of Law in 1993. She also holds a graduate degree from Columbia University and a bachelor of science from Lehigh University.

The initial plea deal came following a five-year Justice Department probe.

Federal authorities with the U.S. attorney's office in Delaware, led by U.S. Attorney David Weiss, a Trump-era appointee, had been investigating Hunter Biden since 2018.

Prosecutors have examined whether he paid adequate taxes on millions of dollars of his income, including money he made from multiple overseas business ventures. They also explored allegations that Hunter Biden lied about his drug use on a gun application form in 2018, despite later acknowledging that he was addicted to drugs around that time.

In June, Hunter Biden agreed to plead guilty to a pair of tax-related misdemeanors and enter into a pretrial diversion agreement that would enable him to avoid prosecution on one felony gun charge.

After the plea deal fell apart on Wednesday, Hunter Biden entered a not guilty plea to the charges.

Republican lawmakers have for weeks publicly decried the plea agreement as a "sweetheart deal."

Ahead of Wednesday's court appearance, Republicans pressed Noreika to consider denying his plea agreement until the court reviews testimony from a pair of IRS whistleblowers.

According to an attorney for the GOP-led House Ways and Means Committee in court documents filed Tuesday, the two whistleblowers have said the younger Biden "appears to have benefitted from political interference which calls into question the propriety of the investigation."

The White House has repeatedly sought to distance the president from the probe. President Joe Biden has said he and his son never discussed his foreign business dealings and there are no indications that the federal investigation has involved the president in any way.

ABC News' Lucien Bruggeman contributed to this report.