Carolyn Piksa was charged with first-degree assault in the March 8 wounding of 65-year-old Bill Keller at a parks maintenance building.
Her lawyer, John Henry Browne, said building a case for the not guilty plea starts with Piksa's mental health.
"Getting an evaluation, psychological evaluation is clearly warranted and the first step," Browne said. Getting the results of that evaluation could take 4-to-6 months.
Prosecutors say Piksa also brandished a gun at a female co-worker. She was charged with second-degree assault in that incident.
Keller is still in satisfactory condition at Harborview Medical Center after being shot in the chest. It was Keller, the executive director of the Associated Recreation Council, a nonprofit group that works with Seattle Parks Department, who called 911 to report the shooting.
The shooting prompted the city to temporarily shut down all community centers and put nearby schools in north Seattle on high alert.
Police used Piksa's cellphone signal to track her to her suburban Burien home, just south of Seattle. SWAT team personnel surrounded the house before she was taken into custody.
Piksa is being held on $1 million bail. If convicted, Piksa could face 14-17 years in prison. Her next court appearance is April 8.