Louise, 19, was accused of murdering eight-month-old Matthew Eappen, while working as an au pair in the United States.
Cheshire County Council hired a Liverpool barrister to prepare David Hudson and Elizabeth Lord for their brief appearances to give character evidence during the hearing in Boston, Massachusetts.
Joan Feenan, county education officer for support services, said: "Both headteachers came to us for help. What was a problem for them was knowing how to give evidence to an American court without causing offence or breaching rules and regulations.
"Our legal services department contacted a Liverpool barrister who was an expert in criminal law and had knowledge of the US court system. He was able to brief them."
Mrs Lord, head of Helsby High School and Mr Hudson, former head at Elton Junior School, agreed to a request from defence lawyers to be character witnesses.
Louise, who is from Elton, spent her early life at her village school, where Mr Hudson was her headteacher for two years. She then went to Helsby, where she spent seven years and gained three A-levels.
Mrs Lord took to Boston seven years of school diaries recording daily problems. Louise did not feature in them.
Mr Hudson, writing in a village newsletter, said: "The line of questioning is very tight. Character witnesses have to keep to a defined style of answering: you are not free to just say whatever you want. I found this frustrating. There was so much to say about the girl that I remember so well."
Curbs on au pairs, page 16