Ross and her lawyer, Stephen Paul Barnard, are seeking to have the results of several breath tests tossed out. They appeared in court Monday to argue their case.
Ross was cited Dec. 30 and faces three DUI-related charges. She has pleaded innocent.
Police said she had a blood alcohol concentration of 0.20 percent. The legal limit in Arizona is 0.08 percent.
Ross, wearing a black pantsuit and silver bracelets, testified for about 10 minutes.
"I felt a threatening tone from him. You know, like a command, a demand," Ross said, referring to Tucson police Officer Scott Sullivan.
Barnard refused comment after the hearing.
According to the police report, officers at the scene wrote that the singer was unable to walk a straight line and fell while trying to stand on one leg and count to 10.
The 58-year-old pop diva has a home in Arizona.
Born Diana Earle in Detroit, Ross is one of the most successful female singers of the past 40 years. With three friends, she formed the Primettes in 1959, which became The Supremes upon signing a Motown recording contract the following year. The act became a trio when one of the women left in 1961, and went on to record such songs as "Baby Love" and "Stop! In the Name of Love." At one point, The Supremes had five number-one hits in a row.
She then launched a solo act in late 1969 and had the number one hit "Ain't No Mountain High Enough" in July 1970. Other solo chart-toppers include "Touch Me In The Morning," "Do You Know Where You're Going To?" and "Upside Down."
In 1972, she branched out into acting, with the lead in "Lady Sings The Blues," the film biography of legendary singer Billie Holliday. Other films include "Mahogany" and "The Wiz."
In 2000, she attempted a "reunion" concert tour with The Supremes, but neither Mary Wilson nor Cindy Byrdsong were included. Instead, the other two singers had performed with The Supremes, but only after Ross had left. The tour flopped.