The laptop’s cameo appearance, after making a similarly brief appearance the day before, underscored how anticlimactic its role has been in the various investigations relating to the conduct of what right-wing critics term “the Biden crime family.” House Republicans failed to glean from its contents anything warranting impeachment of President Biden, the defendant’s father. Nothing has yet emerged from it that ties the son to criminal activity other than drug-related misadventures to which the younger Mr. Biden has already confessed.

The government’s case against Mr. Biden, who has been charged with illegally purchasing a gun, centers on whether he lied on a federal firearms application when he said he was not abusing drugs.

In the trial, the government’s case has relied mainly on bank statements, descriptions from Mr. Biden’s own memoir and data procured from his iCloud account. Up until now, far more attention has been paid to two other key possessions of the defendant: the .38-caliber Colt Cobra revolver he bought on Oct. 12, 2018, and his Ford Raptor truck, in which his brother’s widow, Hallie Biden, discovered the gun and, fearful that Mr. Biden would use it to take his own life, threw it in a trash can at a Wilmington grocery store, setting off a chain of events that led to Mr. Biden’s indictment last September.

The laptop, which Mr. Biden left unclaimed at a Wilmington repair shop and which made its way to allies of President Donald J. Trump a month before the 2020 election, was implicit, however, in testimony on Wednesday from Mr. Biden’s former girlfriend Zoe Kestan. During her 11 months with Mr. Biden, Ms. Kestan told the court, Mr. Biden was addicted to crack and single-mindedly focused on scoring and doing drugs. She said he faithfully carried with him an armada of paraphernalia: pipes, butane lighters, pen caps and chopsticks to clean the pipes, and baking soda to help convert powder cocaine into crack.

As dedicated as he was to his addiction, Mr. Biden was correspondingly hapless with his electronic equipment. During that same period, Ms. Kestan testified, Mr. Biden lost “five or six iPhones” and left a laptop behind at a hotel. His phones and laptops were chronically in disrepair, necessitating trips by her to an Apple Store. She finally relinquished her laptop to her boyfriend when two of his would no longer work.