A verdict is expected later on Thursday, a step that could pave the way for an extraordinary US-Russia swap including Griner and an imprisoned Russian who was once one of the world's most prolific arms dealers.
Griner, a two-time Olympic gold medallist and a Women's National Basketball Association (WNBA) star, was detained at Moscow's Sheremetyevo airport on February 17th with vape cartridges containing hashish oil in her luggage.
Cannabis is illegal in Russia for both medicinal and recreational purposes.
"In sprinting there is Usain Bolt, in Formula 1 – Michael Schumacher, and in women's basketball there is Brittney Griner," her lawyer Maria Blagovolina, partner at Rybalkin Gortsunyan Dyakin and Partners law firm, said in her closing argument.
Griner added in her closing remarks: "I made an honest mistake and I hope that in your ruling, that it doesn't end my life here."
If the court does deem it necessary to punish her, Blagovolina said, then she should receive the most lenient punishment. Alexander Boikov, her other lawyer, said some of the case files were drawn up in violation of the law.
Griner, who plead guilty, did not intend to bring cannabis into Russia, her defence team said.
Speaking of why she pled guilty, the WNBA star said: "My parents taught me two important things: one, take ownership of your responsibilities and two, work hard for everything that you have. That's why I pled guilty to my charges."
The cartridges threw the Texan athlete into the geopolitical maelstrom triggered when President Vladimir Putin sent troops into Ukraine on February 24th.
During the most strained US-Russian relations since the 1962 Cuban missile crisis, U.S. President Joe Biden is under pressure to intervene on behalf of detained Americans - including Griner.
The United States has said Griner was wrongfully detained and made what Secretary of State Antony Blinken called a "substantial offer" to Moscow to exchange Russian prisoners for American citizens held in Russia, including Griner and former Marine Paul Whelan.
One source familiar with the situation said that Washington was willing to exchange convicted arms trafficker Viktor Bout, whose life helped inspire the 2005 Hollywood film "Lord of War", starring Nicholas Cage.
Russian officials have said a deal has not been reached. They argue that Griner - known as BG to basketball fans - violated the country's laws and should be judged accordingly.
Alexander Boikov, a lawyer for the defence, said on Thursday during closing arguments in her trial that some of the case files in relation to Griner were drawn up in violation of the law.