How Hallie Biden is connected to the Hunter Biden gun trial

Hallie Biden, widow of the president's late son, Beau, plays a key role in the backstory to Hunter Biden's trial on federal gun charges that begins this week. And her potential testimony is expected to be critical in his trial. 

Jury selection in Hunter Biden's trial began Monday in Delaware. The president's surviving son is accused of making a false statement material to a firearms sale, making a false statement in a firearms transaction record, and violating a law barring drug users from possessing a firearm. At the time, prosecutors allege Hunter was addicted to crack cocaine, but claimed otherwise. Hunter Biden's history with drug addiction has been a source of pain for his family, as well as a political headache for President Biden.