Griner arrived at the court in Moscow wearing a black Nike ‘Phoenix basketball’ hooded sweater and flanked by security personnel.
She was escorted through a corridor filled with news media, and into a defendant's cage inside the courtroom.
The WNBA star pleaded guilty earlier this month in a trial that has underscored the frayed relations between Washington and Moscow and led to growing calls for the United States to do more to secure her release.
Griner, 31, was detained in February at Moscow’s Sheremetyevo Airport after Russian authorities said they found vape canisters with cannabis oil in her luggage. Medicinal and recreational cannabis are legal in many U.S. states, but both are prohibited in Russia.
A center for the Phoenix Mercury and a two-time Olympic gold medalist, Griner's lawyers argue that she packed her bags quickly and didn’t intend to bring the vape cannisters into Russia.
In her previous appearance of the weekslong proceedings at Khimki regional court near Moscow, her defense team argued Tuesday that, like many international athletes, she uses medicinal marijuana to help with injury pain.
Wednesday's hearing started around 3 p.m. local time (8 a.m. ET), and opened with Griner being cross-examined by the defense.
She told defense lawyer Maria Blagovolina of how, after she went through passport control and security at the Moscow airport on Feb. 17, a staff member with a dog asked her to open her bags, before finding two cartridges.
Another worker “opened the cartridges, smelled them” and then her passport was taken and she signed some documents that she needed Google translate to understand, Griner said. There was an interpreter but she didn’t explain what she was signing, and she was never read her rights, she added.
By this time she had missed her connecting flight to Yekaterinburg, the central city where she plays basketball in the Russian premier league. She called her lawyer, but her phone was then confiscated and her lawyers were not allowed to see her until the early hours of the next morning, Griner told the court.
"At that point it felt like I was being held against my will," she said. "I asked again what's going on and when can I see my lawyer. I was then told I have to be interrogated."
She was then cross-examined by the prosecution, which asked her whether she pleaded guilty to drug smuggling.
"I do understand charges against me, I do take responsibility for them being in my bag, but I didn’t plan on bringing anything to Russia," she told the court.
The hearing finished around 5:30 p.m. local time (10:30 a.m. ET), with the next one scheduled for August 2.
Her trial comes at a particularly sensitive moment between Russia and the West after the Kremlin's invasion of Ukraine.
U.S. officials, including Secretary of State Antony Blinken, have said Griner is being “wrongfully detained,” and supporters fear she is being used as a political pawn by Russia.
On Tuesday, Trevor Reed, a former U.S. Marine freed from a Russian prison in a prisoner exchange in April, said he believes President Joe Biden isn’t doing enough to bring her home.
“In my opinion, the White House has the ability to get them out extremely fast, and they clearly have chosen not to do that. So no, in my opinion, they’re not doing enough,” Reed said in an exclusive interview with “Hallie Jackson NOW,” also referring to corporate executive Paul Whelan, who was detained by Russia in 2018.
The White House on Tuesday responded to Reed’s comments by saying Griner and Whelan have “been top of mind for the president and for our national security team.”
“President Biden has been clear about the need to see every American who is wrongfully detained or held hostage abroad released, including Brittney Griner,” Adrienne Watson, White House spokesperson, told NBC News.
Earlier this month Griner wrote a letter to Biden, telling him, "I’m terrified I might be here forever." Blinken tweeted after a recent hearing that U.S. embassy officials attending the trial were able to speak to Griner and deliver a letter in response from Biden.
The Russian Foreign Ministry has rejected the idea that Griner has been wrongfully detained, saying that the legality of medicinal cannabis in some U.S. states has no bearing on Russia.
“If a U.S. citizen" was "smuggling drugs, and she does not deny this, then this should be commensurate with our Russian local laws, and not with those adopted in San Francisco, New York and Washington,” Foreign Ministry spokeswoman Maria Zakharova said.
“If drugs are legalized in the United States, in a number of states, and this is done for a long time and now the whole country will become drug-addicted, this does not mean that all other countries are following the same path,” she added.
Washington has not officially commented on any possible prisoner swaps for Griner, despite speculation in Russian state media in May that she could be exchanged for convicted Russian arms dealer Viktor Bout, who is serving a 25-year prison sentence in the U.S.
NBC News wasn’t able to confirm those reports.
Tatyana Chistikova reported from Moscow, and Alexander Smith and Yuliya Talmazan reported from London.