Daifallah chose to defend himself in court
An Algerian chemist has been found guilty at Bristol Crown Court of contaminating food and wine by using his own urine and faeces.
Sahnoun Daifallah, 42, of Bibury Road, Gloucester, was found guilty of four counts of contaminating goods at four businesses in May 2008.
Daifallah, who had defended himself, had pleaded not guilty to all charges.
Sentencing was adjourned to allow preparation of psychiatric reports. Daifallah is likely to be deported.
Judge Carol Hagen said: "I find this a very worrying case and the circumstances are alarming."
She warned Daifallah that if he did not cooperate with authorities in creating pre-sentence reports, it would "reinforce my conclusion that I find you to be a potentially very dangerous man".
The court had heard the Algerian-born chemist sprayed the mixture in the Air Balloon Pub, in Birdlip, near Cheltenham on 14 May.
He then moved on to the Waterstones bookstore in Cirencester, Tesco in Quedgley and Morrisons in Abbeydale.
The court heard shoppers and staff in both stores saw Daifallah with a black lap top computer with a vapour coming from the bag being sprayed on the shelves.