A prominent San Francisco Bay-area civil rights attorney says the foster father of a missing 5-year-old boy with cerebral palsy will take a polygraph test.

Attorney John Burris said Wednesday that Louis Ross, foster father of missing Hasanni Campbell, has agreed to take a polygraph test. Ross was the last person to see Hasanni, who has been missing since Monday.

Ross has told police he left Hasanni sitting in his car parked around the corner from an Oakland shoe store where Jennifer Campbell, who is Ross' fiancee and the boy's foster mother, works.

Ross said he was unlocking the store door to give the boy, who wears braces on his legs, easier access. He said the boy was gone when he returned.

Burris told the Oakland Tribune he has given advice to the Fremont couple but has not been retained as their attorney.