In three different British courtrooms yesterday, three ordinary people stood accused of three very different crimes, but all based simply on their opposition to the war in Iraq.

In the first case of its kind, a woman received a criminal conviction for standing outside Downing Street and reading aloud the names of the 97 British soldiers who have died in the Iraq conflict. At the same time as Maya Evans, 25, appeared in court yesterday to become the first person to be found guilty under the legislation designed to create an exclusion zone around Parliament Square, Douglas Barker, 72, a retired businessman from Wiltshire, was told by a magistrate that he faces jail for withholding part of his income tax on his investments, also in protest over Iraq.

In a third courtroom in Aldershot, a military judge heard that Flight Lieutenant Malcolm Kendall-Smith, 37, an RAF medical officer based in Scotland, faced a court martial for refusing to serve in Iraq on the basis that the war was illegal.

After her hearing, Ms Evans, a part-time vegan chef from Hastings, described her conviction as an assault on her right to freedom of expression. She said: " I just think it's a shame you can't voice your freedom of speech in this country any more and it is illegal to hold a remembrance ceremony for the dead." Earlier, she had told Bow Street magistrates: "I didn't want to be arrested but, as far as I was concerned, I didn't think I was doing anything wrong standing there on a drizzly Tuesday morning with a colleague reading names of people who had died in a war. I don't think it's a criminal offence and I don't think I should have been arrested for it."

After a three-hour hearing, she was found guilty of breaching Section 132 of the Serious Organised Crime and Police Act 2005; she was given a conditional discharge and ordered to pay £100 costs. The law, which came into power in April, makes it illegal to hold an unauthorised protest within 1km of Parliament Square. It was introduced partly to get rid of a long-term and noisy peace protester, Brian Haw, whose one-man vigil outside the gates of the Palace of Westminster was considered a nuisance.

Ms Evans was arrested, along with follow demonstrator, Milan Rai, in October as they stood next to the Cenotaph, close to the gated entrance to Downing Street. Mr Rai, 40, a writer, was reading out the names of dead Iraqi civilians. The pair had been intending to ring a bell for each of the names read out. Mr Rai, who had spoken to the police in advance about his protest, was not charged.

In Chippenham, magistrates were told that Mr Barker was refusing to pay £1,142.58, which amounted to 10 per cent of the income tax he was due to pay for the second half of this year. Instead, he had put the money to one side, intending to give it to a charity supporting children in Iraq, and had sent a note to the Inland Revenue to explain.

Mr Barker, of Purton, Wiltshire, told the magistrates: "I estimated that 10 per cent goes on military expenditure and I came to the conclusion that by paying this I was violating my conscience because I felt it would have been used illegally to kill people in a sovereign state."

He said he would only pay if he got a promise the money would not be used for military purposes, adding he believed the Government had used illegal weapons against Iraqi civilians since the start of the war. His comments were greeted with applause from a group of about 20 anti-war protesters in the public gallery.

Magistrates imposed a liability order, which means he has to pay the outstanding amount or bailiffs will become involved. Hilary Light, the chairwoman of the bench, said: "Whatever this court may feel, our jurisdiction is laid down and we can't say where money can go to. We are therefore going to make the liability order.'' No time limit was given.

Mr Barker, who helps run his son's organic farm, said afterwards that he would probably send the money to a government department that did not have any dealings with military expenditure, such as the NHS. "I don't think they will go so far as to send me to prison, they will either accept the money that way or just send the bailiffs round.''

Mr Barker, who did his National Service in the RAF, formerly ran a travel company, which he sold in the late 1980s. He said he was a lifelong socialist who had supported Tony Blair when he was first elected, adding: "I was very unhappy about the war when it began, but I might have given him the benefit of the doubt if things had gone well. But I think it's been a complete fiasco.''

At a hearing in Aldershot, Flt Lt Malcolm Kendall-Smith was told that he faces a two-day court martial for refusing to serve in Iraq.

Flt Lt Kendall-Smith, a unit medical officer based at RAF Kinloss, Morayshire, Scotland, had already completed two tours of Iraq. However, after studying the legal position, including the advice of Lord Goldsmith, the Attorney General, he concluded the war was unlawful and he should not return.

David Perry, for the prosecution, said there were two questions relevant in the case. Firstly, was it lawful to ask Flt Lt Kendall-Smith to return to Iraq? Secondly, were each of the four charges he faced relevant to the order telling him to go back.

His lawyer, Philip Sapsford, did not dispute his client failed to stay for a training course, helmet-fitting, an employment briefing and initial risk training exercise. But, Mr Sapsford argued the officer did not break English law. "The crucial question is whether to go to Iraq and the war itself is in fact unlawful in international law," he said. "I ask this question because UN resolutions do not form part of English law."

Flt Lt Kendall-Smith faces five charges of disobeying lawful orders under the RAF Act 1955. The court martial will begin on 15 March.