Thomas Black, 73, former head of biology at St Mungo’s High School, is accused of sex offences against four pupils between 1978 and 1995.
The trial, previously delayed because of the coronavirus pandemic, had been set to start later this month.
However, it has now been decided that Black cannot stand trial because of his deteriorating physical health, including serious breathing and mobility issues.
It had been proposed that he could go on trial from his living room, linked up by video to the courtroom, but this has been ruled out because his health problems would result in constant disruptions to the proceedings.
A hearing on Black’s health at Dunfermline Sheriff Court heard evidence from Jesse Dawson, Professor of Stroke Medicine and consultant physician at the Queen Elizabeth University Hospital, Glasgow.
He told the court that Black’s physical health had deteriorated significantly over the past year.
After hearing from the professor, Sheriff Charles Macnair ruled that Black was unfit to stand trial because of his poor state of health.
Instead, an examination of facts will take place at the court on January 31 when witnesses will give evidence but there can be no conviction under this procedure.
Black denied the four charges against him.
It is alleged on a single occasion between August 1985 and May 1987 at the school he indecently assaulted one boy, then aged 15 to 17, by touching his privates parts over his clothing.
It is further alleged on various occasions between January 1989 and May 1991, again at the school, he touched and rubbed the body and private parts of another boy, then aged 15 to 17, through his clothing, and did the same to a third boy, aged 14 to 18, between August 91 and December 1995.
In the case of the third boy, it is alleged Black also indecently assaulted him while travelling in a car in Falkirk, and that he once removed the boy’s private parts from his clothing before committing a sexual act upon him.