Nicholas Evans, the stipendiary magistrate at Bow Street magistrates' court in London, told the three students and a college lecturer that "no rational person" could accept their argument that their actions were designed to prevent the Cabinet minister from breaking the law by inciting racial hatred.
He said the demonstration, mounted by the Movement for Justice after the State Opening of Parliament last November in protest at the Government's Asylum and Immigration Bill, had clearly been planned and had left both Dr Mawhinney and his wife distressed.
A barrage of plastic bags and flour was hurled at Dr Mawhinney and his wife as they left the Houses of Parliament and walked across nearby College Green on their way to an interview at a temporary BBC television studio.
Their actions were captured on television film, which was shown to the court.
Allowing the defendants bail until 14 May when he will pass sentence, Mr Evans warned them that they each faced the risk of being jailed.
Karen Doyle, 19, of Camden; Naveed Malik, 18, of Clapton; Amanda Egbe, 20, of Stoke Newington and Anthony Gard, 54, a teacher from Brockley, all in London, were convicted of one charge of common assault against Dr Mawhinney, a similar offence against his wife Betty, and a general allegation of using threatening behaviour.
A fourth student, Nicholas de Marco, 29, of Clapton, east London, was cleared of all three charges. The former philosophy and history student, was president of the students' union at Kingsway College, Camden, north London, until he was expelled earlier this year.
Dr Mawhinney had to run a gauntlet of placard-waving demonstrators, chanting "racist, racist" as he arrived and left the heavily policed court building.
- More about:
- City Of Westminster Magistrates' Court
- Higher Education
- University Of The Arts London