"Some might ask 'Why didn't you give the money back?'" Thomas said in his opening statement Wednesday. "Because it was sent anonymously."
Lisa Riggs, a lawyer for Brooks, told jurors the hospital lured the singer, deliberately and falsely claiming it would build the women's center and display Colleen Brooks' name "like the Hollywood sign in Los Angeles."
"This is not what Garth Brooks had bargained for," Riggs said. "Over six years after the donation, nothing is named after Colleen Brooks.
"It was a simple deal: $500,000 and mom's name is on the women's center," Riggs told jurors. "In (Brooks') words, it was an easy deal to get done."
Moore, the trial's first witness, said under questioning by the singer's lawyers that he knew a women's center would be more appealing to Brooks than having his mother's name on an intensive care unit.
"We knew he was very passionate about his mom and we were passionate about women's issues," Moore said.
Brooks attended the trial with his wife, country singer Trisha Yearwood. The couple lives near Owasso, a Tulsa suburb, about 130 miles northeast of Yukon.
Colleen Brooks died of cancer in 1999.