The muted mood of Hunter Biden’s trial, which had focused on his struggle with addiction, shifted abruptly on Wednesday, with the appearance of Zoe Kestan, a former girlfriend who described him as a charming free-spender who loved the party-hopping high life in New York.
Ms. Kestan, a dancer Mr. Biden met at a gentleman’s club in 2017, said the two immediately connected — “catching feelings” as she put it — after they sat in a quiet back room and he clicked on a song from Fleet Foxes, an indie rock band, to remedy the silence.
Her entrance produced one of the more awkward moments in a trial already brimming with them. When Leo Wise, the lead prosecutor, asked her to identify to Hunter Biden in the courtroom for the record, he offered an uncomfortable wave, and a fleeting smile before looking down, head in hands.
Ms. Kestan’s testimony was sympathetic to Mr. Biden, and reaffirmed the portrait of a tortured addict reeling from family tragedy and burdens of living up to his famous family name. At several points, she described wanting to help him with various attempts at sobriety, even as she had observed him repeatedly smoking crack — chipping off small crystals from an enormous rock of crack she said was the size of a Ping-Pong ball.
But it was not all abject misery. And her testimony was delivered in an upbeat, optimistic tone.
In a bit of prosecutorial stage-managing, the special counsel investigating the president’s son summoned Ms. Kestan minutes after brief, somber testimony from Mr. Biden’s former wife, Kathleen Buhle. She testified about the excruciating ordeal of discovering his crack addiction and her efforts to shield the couple’s three daughters from his behavior.
Then Ms. Kestan arrived. As the riveted courtroom listened, Ms. Kestan provided a nearly cinematic rendering of their drug-fueled partying during Fashion Week in Manhattan in 2018. Her testimony, like that of Mr. Biden’s other romantic partners, is intended to establish that he was a chronic drug abuser who lied when he claimed to be clean on an application for a handgun in October 2018.
She said he withdrew enormous quantities of cash from a Wells Fargo A.T.M. in Midtown Manhattan during that week in February 2018, dispatching her to take out the money by reading her a code sent to his phone.
“He used cash for a lot of things, a good amount of it was for drugs,” Ms. Kestan said.
But he gave also her $800 for another purpose — to “buy clothes for his kids” from a high-end retailer.