Tamera Coffee, 34, Warm Springs, pleaded guilty in federal court to charges she killed her foster child last summer by leaving him in a closed car in the hot sun. She pleaded innocent April 17 to the second-degree murder charges filed last year. On the morning she was to go to trial, she accepted a plea agreement and a 6 1/2 year sentence. Coffee admitted she left 4-year-old Andres Saragos in a car for nine hours on July 13, 2000. Temperatures topped 90 degrees that day. Coffee first told police Andres had been home all day, but later admitted she left him in the car with the windows down. After a polygraph test, Coffee changed her story again, telling police she left windows down half an inch and didn't check on the boy. A prosecutor said he had a witness who would have said the windows were completely up. In a written plea to the court, Coffee took full responsibility for the boy's death. Coffee was released until the judge makes a final sentencing decision on July 31. Andres had lived with Coffee and her husband for 21/2 years. He was in and out of foster care while his birth mother, Vernice Switzler, an American Indian, battled alcoholism.