Hunter Biden is on trial in Delaware for charges that stem from a federal probe into alleged firearms violations.

Prosecutors from special counsel David Weiss' office and Biden's defense attorney Abbe Lowell made opening statements after jurors were selected Monday. Biden has pleaded not guilty to federal gun charges.

Following a yearslong investigation, Weiss charged Biden with making a false statement in the purchase of a firearm; making a false statement related to information required to be kept by a licensed firearm dealer; and one count of possession of a firearm by a person who is an unlawful user of or addicted to a controlled substance. 

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On Tuesday morning, prosecutors showed a list of witnesses who may be called to testify. Here is who they are: 

The first prosecution witness sworn in on Tuesday was FBI special agent Erika Jensen. Prosecutors said in a court filing that Jensen will introduce evidence including text messages and admissions in his memoir, "Beautiful Things," which the government says shows Biden was using illicit drugs at the time he purchased a firearm. 

The indictment of Biden said that he certified on a federally mandated form "that he was not an unlawful user of, and addicted to, any stimulant, narcotic drug, and any other controlled substance, when in fact, as he knew, that statement was false and fictitious." 

Biden and Kathleen Buhle were married from 1993 to 2017. Buhle has spoken publicly about Biden's drug addiction and many affairs, including his sister-in-law and widow of his late brother, Beau, Hallie Biden, who is also a witness for the prosecution. Buhle detailed difficulties in her marriage to Biden in a 2022 memoir titled, "IF We Break: A Memoir of Marriage, Addiction, and Healing." 

Prosecutors said that throughout 2018, Buhl would search Biden's car because "she did not want their children in a vehicle with drugs." She found drugs or drug paraphernalia about a dozen times, according to court documents. A 2018 text message exchange with Biden said, "I also found a few crack pipes. I took them out because our daughter was driving the car," according to prosecutors.

Zoe Kestan is another former romantic partner of Biden. Prosecutors hope Kestan will highlight the first son's former use of crack cocaine, "every 20 minutes except when he slept." They allege Kestan visited Biden in Massachusetts when he was in rehab in the fall of 2018, after he purchased his gun, and observed him using drugs.

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Prosecutors will also call Biden's sister-in-law, Hallie Biden, to testify about his drug use. The pair were in a romantic relationship in 2018. Hallie Biden observed Hunter using drugs on multiple occasions, according to prosecutors, and she and her children discovered drug paraphernalia and drugs in his possession when they searched his bags, backpacks and vehicle in an effort to help him get sober.

Hallie Biden, identified as Witness 3, "observed that the defendant frequently lost phones and changed phones, which explains gaps in time where there are no messages, and she also had various text message exchanges with the defendant," prosecutors said.

Gordon Cleveland is an employee of Starquest Shooters and Survival Supply in Wilmington, Delaware, who sold Biden a gun. He will be called to testify that Biden purchased a Colt Cobra 38SPL revolver, a HKS Speedloader for the .38 special and 25 rounds of Hornady "American Gunner" ammunition. 

Cleveland is expected to tell jurors that Biden completed ATF Form 4473, federally required background check paperwork, which asked whether he was an unlawful user of, or addicted to, any depressant, stimulant, or narcotic drug, or any other controlled substance, and that Biden lied and answered, "no." If Biden had answered, "yes," the gun seller could not have sold him a gun, prosecutors said.

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Delaware State Police Senior Corporal Joshua Marley will testify about his response to an incident at Janssen's Market, Biden's admissions and about evidence recovered, prosecutors said. 

The gun Biden purchased was discovered in a trash can outside Janssen's Market, a grocery store in Greenville, Delaware, in 2018. According to a police report, Hallie Biden allegedly took Hunter's gun and threw it in a trash can behind the store, which was located across the street from a high school. She later returned and found the gun missing, Politico reported.

Former Delaware State Lieutenant Millard Greer will testify about his recovery of the gun, ammunition, speedloader and brown leather pouch from the man who found them in the trash receptacle at Janssen's Market, prosecutors said.

Prosecutors may call DEA Supervisory Special Agent Joshua Romig as an expert witness on "coded messages" allegedly sent by Biden, which will prove his drug use and support the government's allegation that Biden lied on a federal gun form. 

A forensic chemist, Dr. Jason Brewer, will be asked about his analysis of the brown leather pouch that allegedly belonged to Biden and his opinion that the residue is cocaine based on his testing and evidence, prosecutors said. 

Fox News' Aubrie Spady contributed to this report.