Hunter Biden was found guilty on three counts related to illegal gun possession.

The jury’s verdict, reached after about three hours of deliberation, followed a week-long trial in the Biden family’s hometown of Wilmington, Delaware, that featured sometimes excruciating testimony about his addiction habit, much of it from some of his closest relatives.

It followed a decision by Hunter Biden, the oldest living son of Joe Biden, not to take the witness stand in his own defence.

He was accused of making two false statements when filling a form to buy a Colt revolver in October 2018: first by stating untruthfully that he was not addicted to or using drugs, and then by declaring the statement to be true. A third charge alleged that he then illegally owned the gun possession for 11 days, before his sister-in-law and then lover, Hallie Biden, threw it in a trash bin in panic.

Abbe Lowell, Hunter’s principal lawyer, argued that the prosecution had provided no evidence that he had taken crack cocaine – to which he later admitted in a memoir to having been addicted before going into rehabilitation – in the month that he bought and owned the gun.

The defence lawyer also established that no one had seen Hunter use the drug in that period.

But messages retrieved from Hunter’s mobile phone undermined the argument that he had not been ingesting drugs in the period before and after purchasing the weapon. The day after he bought the gun, he sent a text to Hallie Biden saying he was meeting a known drug dealer called Mookie. Then, a day later, he revealed in another text that he was sleeping on a car and smoking crack.

His daughter, Naomi Biden Neal – testifying in his defence – told the court that her father had seemed sober in the weeks before the purchase. But the prosecution introduced more text messages that betrayed a strained and fraying relationship between the pair, including one in which Naomi told her father he had driven her to breaking point.

The prosecution called other members of the Biden family, including his former wife Kathleen Buhle, to whom he was married for 24 years, and Hallie Biden, the widow of his brother Beau, as it tried to show that Hunter’s drug use continued during 2018 and 2019.

The testimony painted a portrait of Hunter Biden falling deeper into addiction as he struggled to cope with the death of Beau, who died from brain cancer in 2015.

After the breakup of his marriage, he formed a romantic relationship with Hallie Biden, who admitted to having smoked crack with him.

Summing up on Monday, prosecutor Leo Wise said Hunter Biden’s text message showed him trying to make drug deals before and after his gun purchase.

Calling the evidence against the defendant “personal, ugly and overwhelming”, he noted that Hunter Biden told Hallie Biden on 14 October 2018, two days after buying the gun, that he had been smoking crack. “That’s my truth,” he quoted Hunter as writing.

“Take the defendant’s word for it. That’s his truth,” Wise said, urging them to reject defence suggestions that Hunter Biden was simply trying to avoid being with Hallie Biden. “You don’t leave your common sense behind when you come into that jury box.”

The evidence had included lurid testimony of Hunter Biden smoking crack pipes, backed up by photographs shown in court.

Zoe Kestan, Hunter’s former girlfriend who met him at a gentleman’s club, told the court last week that he frequently withdrew money to fund drug purchases.

She said he would smoke what she presumed was crack “every 20 minutes or so” and that she had seen him smoke it over several days in Malibu, California, in September 2018, the month before he bought the gun.

Related: Hunter Biden gun trial: key takeaways from the first week

The proceedings were witnessed by Hunter’s stepmother, Jill Biden, the first lady, who was present every day apart from last Thursday, when she flew to Normandy in France to attend the 80th anniversary of D-day with her husband.

Wise pointed to the gallery, where Jill Biden sat with Hunter’s wife, Melissa Cohen Biden and other family members, and told the jury not to be influenced.

“All of this is not evidence. People sitting in the gallery are not evidence,” he said.

Lowell, for the defence, took the opposite tack – telling jurors that the fact that Hunter Biden had a famous last name did not mean he was less entitled to his rights than any other defendant and urging them to find him not guilty.

He argued that there was no evidence that Hunter Biden had ever taken the newly-purchased gun out of the locked box it came in before Hallie Biden found it and threw it in a bin near a grocery store in Wilmington.

In a passage that crystallised how the trial had pitted members of the Biden family against each other, he said: “On October 23rd, Hallie did something incredibly stupid,” Lowell said, referring to her disposal of the weapon.

“She may have done it for love,” he added, or out of anger after suspecting that Hunter Biden had been with another woman.

He also contested the assertion that large cash amounts withdrawn by Hunter Biden had been used to buy drugs, saying the prosecution had not supported this claim with detailed financial records.