When two police officers came to interview Jamie Bauld, a polite, friendly Down’s syndrome boy with a mental age of about 5, he welcomed them with a big smile and a handshake. As the officers read him his rights and charged him with assault and racial abuse, he agreed with everything they said, then thanked them for coming to see him.

Yesterday Jamie’s parents told The Times that they had been through a seven-month ordeal with the Scottish legal system over what they described as a minor fracas between two youngsters with learning difficulties.

Jamie, 18, cannot tie his shoelaces or leave home on his own, nor can he understand simple verbal concepts such as whether a door is open or shut. But his parents said that he was charged with attacking a fellow student, an Asian girl who also had special needs.

Jamie’s parents described as “utterly ridiculous” the actions of the authorities in bringing adult charges against their son, who they said was not only innocent, but unable to comprehend why he had been in trouble.

They believe that he was a victim of the zero-tolerance policy on racism under which police have to respond to any complaint, however minor.

Experts in Down’s syndrome say that the case shows insensitivity and is an example of bureaucracy gone mad.

The incident in question took place last September at the special needs department of Motherwell College, in Lanarkshire, where Jamie is a student. Fiona Bauld, Jamie’s mother and full-time carer, claimed that the Asian student, who is only slightly older than Jamie, had been following her son and staring at him. Jamie had earlier complained to his parents that her behaviour scared him, and they had advised him just to walk away.

But one day, his mother said, the girl came close up to Jamie as he was eating lunch. He pushed her with one hand and told her to go away.

“It was,” Mrs Bauld said, “like two five-year-olds having an argument.” It was, therefore, no surprise when she received a phone call from the college to say that Jamie had been told off for pushing the girl, and that the girl had been reprimanded as well.

Soon after, however, the Baulds heard that a notice had been placed in a Motherwell newspaper asking for witnesses to a “racial assault” at the college on the day in question. It is not known who placed the advert but afterwards two police officers came to Jamie’s house in Condorrat, Lanarkshire, and interviewed him.

Jim Bauld, Jamie’s father, who was present at the interview, said: “They asked Jamie if he had slapped the girl on the face and he said yes, because he thought that was what they wanted him to say – because Down’s syndrome [people] always try to please.

“I asked them if they had any experience of Down’s syndrome. I had no idea they were going to charge him. I sat and listened in absolute disbelief when they read him his rights and charged him.

“I said it was ridiculous, he didn’t even understand simple things, like inside and out, upstairs and downstairs, whether a door is open or shut, and they were reading him his rights and he was saying, yes, he understood. Then he shook their hand and thanked them.”

The officers, Mr Bauld said, were very pleasant and told him not to worry “because the case would come to nothing”. They told him they would explain to the Procurator Fiscal that Jamie had Down’s syndrome, and that the Asian girl had admitted that she had scratched her own face to mark it and referred to herself as “blackface”.

Shortly after the visit came a letter from the Procurator Fiscal in Hamilton saying that the authorities now had enough evidence to charge Jamie. Mrs Bauld phoned the Procurator’s office and asked them if they knew Jamie had Down’s syndrome. She claimed officials refused to discuss the case with her. The Procurator Fiscal’s office denied this and said that the family were kept informed throughout the process.

In December, Mr and Mrs Bauld asked their lawyer to write to the Procurator Fiscal to explain the situation. They did not receive a reply.

It was 7½ months after the initial incident when they received a brief letter from the Procurator Fiscal to say he would not be proceeding with the prosecution. There was no apology.

Mrs Bauld said: “The incident was blown out of all proportion. I can’t believe that two special needs people should be dealt with like this. The whole thing was handled so badly.”

A spokeswoman from Down’s Syndrome Scotland said: “I have never met any Down’s syndrome [people] who are racist. This incident should have been contained within the college. It has been very badly handled.”

Annabel Irvine, the former head of Glencryan special needs school, who taught Jamie, said: “They have been through absolute agonies. Jamie is the most polite, well-mannered boy.”

A spokesman for the Crown Office said: “There were a number of further inquiries which required to be made by the Procurator Fiscal before a final decision could be taken in this sensitive case. We were fully aware of the family’s anxieties about this matter, and the Procurator Fiscal kept the family informed throughout.”

A spokeswoman for Strathclyde Police said: “All we can say is that on September 4, 2007, an 18-year-old was reported to the Procurator Fiscal in connection with an alleged incident of assault and breach of the peace at Motherwell College.”

The spokeswoman said the force recognised that special care and understanding were required when dealing with “mentally disordered persons”.