James Forster is alleged to have terrorised villagers
Dr James Forster is alleged to have conducted a 12-year campaign against the residents of Manfield.
People in the picturesque village near Darlington received a series of lurid letters between 1987 and 1999.
Teesside Crown Court heard that an old woman was threatened with a bomb and a 13-year-old girl was sent pornography.
"In all aspects of his professional life I found that he maintained the highest standards of personal discipline.
"His judgement was always sound and respected.
"I have never known him to act rashly or to be anything other than kind and tolerant in his dealings with others.
'Double life'
"I find it impossible to reconcile these characteristics with the nature of the charges levelled against him.
"The allegations against Dr Forster have been explained to me but they do not fit the character of the man I know."
University of Northumbria lecturer Joy Reekie told the court she had known Forster for 20 years both as a friend and as a colleague.
She said: "He was certainly a very reliable, friendly person who worked in a very professional and courteous way."
Prosecutor Michael O'Neill told the jury that Dr Forster led a double life.
He said: "The Manfield letter writer is not some drug-taking 13-year-old with time on his hands or simply some bored housewife.
"It is someone who is highly intelligent and capable of taking the kinds of precautions which we know were taken to avoid discovery."
Dog excrement
Mr O'Neill said it was telling that from the time Dr Forster was first arrested to the time of him coming to court only one letter had been sent to anyone in Manfield.
It was an envelope full of dog excrement.
Dr Forster denied he was obsessed with his neighbours, despite keeping a detailed diary of their every movement.
He claims to have been a victim of the poison pen letters himself.
Dr Forster, from Kirklea, Grunton Lane in Manfield, denies three charges of threatening to destroy or damage property, three of damaging property, three of sending indecent or obscene mail, and one of incitement to commit burglary.
The case continues.