“Among the medical documents is a doctor’s prescription for the substance that, due to an oversight, Brittney Griner left among her belongings when crossing the border,” said Maria Blagovolina, partner at the law firm Rybalkin, Gortsunyan, Dyakin and Partners.

Her other lawyer, Alexander Boykov of Moscow Legal Center, said that Ms. Griner’s prescription was to help her cope with pain. 

Ms. Griner, like many American basketball players, came regularly to Russia during the WNBA offseason, where the players enjoyed lavish pay and treatment. A week after she was arrested at Moscow’s Sheremetyevo airport, Russia invaded Ukraine. It plunged relations between the U.S. and Russia to a new low and also suspended Russia’s participation in international sports.

Her attorneys also submitted tax returns showing that Ms. Griner had paid a large amount of taxes in the Russian Federation as a result of her salary from UMMC Ekaterinburg, the powerhouse team she had played for since 2014.

And they offered letters of support from various organizations in Yekaterinburg, including the team, the Russian Basketball Federation, and USA Basketball, the governing body for whom Ms. Griner was on two Olympic gold-medal winning teams. 

The UMMC Ekaterinburg general manager, team captain and team doctor had testified in Ms. Griner’s defense a day earlier, the general manager emphasizing that with Ms. Griner on board, the team won the EuroLeague championship several times, which allowed more Russian teams to compete in the league, according to its rules. 

Ms. Griner has been charged with two offenses: illegally possessing narcotic substances without the purpose of selling them, and smuggling of narcotic substances in a significant amount, according to her lawyers. 

The total sentence for the charges could be up to 10 years in prison.

Ms. Griner entered a guilty plea last week, telling the court that she had carried the vape cartridges into the country, but that she had packed them in a hurry and didn’t intend to break Russian laws. 

The quantity of hashish oil that Ms. Griner has been accused of carrying could have been legally possessed in Arizona, where she lives, and 18 other U.S. states, according to NORML, an American group that advocates for marijuana drug law changes.

Her lawyers said after the plea that Ms. Griner hoped it would help her in sentencing.

Medical marijuana enjoys relatively little support as a concept among the Russian public, and possession of any amount of marijuana is treated as a serious crime under Russian law. In a poll by state-run pollster VTsIOM in 2018, 89 percent of respondents said they were against the idea of legalizing the drug for medical purposes. 

Ms. Griner’s Friday court session lasted less than an hour, and the trial will resume July 26, when the defense will present further evidence, Mr. Boykov said. 

—Evan Gershkovich contributed to this article.