A St Andrews University student was expelled this week after being convicted of a racially aggravated attack on a 21-year-old Jewish exchange student in the halls of residence in March this year.

His co-defendant, facing an identical charge, was acquitted after the case against him was found to be not proven, but he was nevertheless suspended from St Andrews for a year.

It was a landmark judgment in Scotland after Sheriff Charles Macnair, hearing the case, made clear that he was satisfied it had been a racially motivated, rather than a political, attack.

Paul Donnachie, 19, and Samuel Colchester, 20, were on trial at Cupar Sheriff Court in Fife, Scotland, after an evening of drinking degenerated into a lewd attack on 21-year-old Chanan Reitblat, a Lithuanian-born American chemistry student who was in Scotland for a year as part of his degree at New York's Yeshiva University.

During the attack, Donnachie rubbed his genitals before wiping his hands on an Israeli flag in the room. Mr Reitblat, whose family had left Lithuania when he was a child to escape "severe Jewish oppression," had pinned the flag, given to him by his brother who had served in the Israeli army, above his bed.

Donnachie and Colchester had entered Mr Reitblat's room at 1.30 am on March 12. After the attack, when they jumped on the Jewish student and urinated into his sink, the pair were pushed out of the room, but shouted in the corridor that Israel was "a nation built on terrorism," and "they are all suicide bombers." Mr Reitblat, they shouted, was "a Nazi, fascist and terrorist."

In court, Donnachie, a member of the university's Palestine group, insisted: "Disrespecting the flag is a time-honoured method of expressing one's disapproval with the actions of a state.

"This was a political statement and not about one individual. By displaying a flag of Israel you are making a controversial statement which invites criticism."

Donnachie later acknowledged that he had posted Facebook comments, including one saying: "There is a Zionist in my hall." In another Facebook message he wrote: "I got into sh-t for disrespecting [an Israeli flag]. F--k them. Standing my ground to the end on this one."

Mr Reitblat, who came back from New York to give evidence, told the court that he had felt "utterly violated," and that the offence had left him terrified. He had been so scared by the March events that he had "almost failed" a crucial exam. "I have never been to Israel but am Jewish by descent and firmly believe the Jews have a right to self-determination... and a homeland," he said during questioning. "I displayed the flag of Israel in my room because it is part of my identity."

Mr Reitblat left St Andrews for Glasgow immediately after the attack, taking refuge in the home of the Jewish chaplain, Rabbi Garry Wayland.

Finding Donnachie guilty, Sheriff Macnair said he was not interested in any wider debate about "the Palestinian population in the West Bank and the Gaza Strip. This case is not about the right and wrongs of any actions by the government of Israel," he said.

Sheriff Macnair said he was satisfied that Donnachie's actions were racially motivated, and that he had called Israel a terrorist state and called Mr Reitblat himself a terrorist.

"I consider that you displayed malice toward Mr Reitblat because of his presumed membership [sic] of Israel," he added. During the case the sheriff had refused to allow "expert witnesses," including Mick Napier of the Scottish Palestine Solidarity Campaign (SPSC), to give evidence relating to the political situation in Israel.

Sentencing was deferred until September 13 for reports.

Scottish University Jewish Chaplaincy condemned the role of the SPSC, which demonstrated outside court throughout the case, following the attack. A spokesman said: "Their website campaign, presenting and purporting to justify the attack on Chanan Reitblat on the grounds of legitimate free speech and political expression, is a gross error of judgment which does not help the Palestinian cause. What freedom of speech and political expression?

"By putting the Jewish student in such a state of fear and alarm that he felt the need to leave St Andrews, stay in Glasgow with the Jewish chaplain and return to New York early?"

After the case, Donnachie said he would appeal against his conviction, branding it "ridiculous. The right to criticise Israel, or any state, is very important. It is depressing that somebody who has fought against racism is tarnished in this way."

He complained that his expulsion was "completely disproportionate. Within an hour of the conviction I was told my university career is over."

A St Andrews spokesman said: "The student community at St Andrews has a long tradition of tolerance, respect and the right to freedom of expression.

"However, it is also a community which abhors racial intolerance. While such behaviour is exceptionally rare, the university will always take the strongest possible sanction against it."