The 52-year-old Detroit native told the New York Daily News she had just finished a Broadway play in 1990 when her agent said "'Law & Order' was looking for women and I should try it because the show won't last another year.
"Twelve years later and it surprises everyone," she said, adding she is signed to the show through 2006 playing Lt. Anita van Buren.
She praised executive producer Dick Wolf's insistence on interaction between actors and writers.
"Sometimes it's hard having my voice be heard," she said. "It's very difficult, because you can say something and lose a job. Remember, I'm black and female and Hollywood doesn't understand."
The 12th season's finale will air next Wednesday on NBC.