Nohema Graber, 66, taught at Fairfield High School, which is in the southeastern part of the state. Preliminary evidence indicated that she suffered from "trauma to the head."
She was reported missing last month and her body was located at Chautauqua Park in Fairfield. Authorities said her body was found concealed under a tarp, wheelbarrow and railroad ties.
Willard Noble Chaiden Miller and Jeremy Everett Goodale, both 16 at the time, were charged as adults in the killing. The Associated Press reported that the new details were found in a court filing on Dec. 23. The report pointed out that lawyers for the teens have asked that they be tried as juveniles.
Prosecutors have challenged the request, saying that Goodale, if convicted in juvenile court, would be released in less than 24 months.
Both teens have pleaded not guilty. Authorities have not released a motive.
The Associated Press contributed to this report