Sunday Tribune journalist Suzanne Breen with Tribune solicitor Joe Rice at court on Friday

The Sunday Tribune has received widespread support for its refusal to comply with PSNI demands that its Northern Editor hand over phones, computers, and other material relating to stories on the Real IRA.

Respected journalists, along with victims of paramilitary violence, have backed the newspaper's stance. The PSNI is seeking a court order under the terrorism act to seize the material that Suzanne Breen has refused to give detectives.

The case, which opened on Friday, will resume in Belfast on Tuesday. Breen potentially faces up to five years' imprisonment for not complying. The material relates to the Real IRA's claim of responsibility for murdering two British soldiers at Massereene, and an interview with an army council representative.

Channel 4 News' chief correspondent, Alex Thomson, who was threatened with legal action for not divulging sources to the Bloody Sunday inquiry, said he stood shoulder-to-shoulder with the Sunday Tribune.

"The danger in such approaches by the state is that the freedom of people to come forward and divulge information to reporters on the condition of anonymity is damaged," he said. "It might be the Real IRA this week – but, next week, it could be a nurse, school teacher or soldier disclosing grave wrong-doing at real risk to their career or safety."

The Sunday Times' Liam Clarke described the PSNI's action as "a cruel, expensive farce". He said if Breen complied, her life would be in danger and she would have to leave Northern Ireland.

Clarke criticised the PSNI chief constable: "If Hugh Orde wants to go to his new job as president of the Association of Chief Constables as the man who rolled back press freedom and jailed the mother of a young child for refusing to put her life on the line and ruin her career for him, then he is welcome to tilt at the windmill. But I doubt the courts will join him."

Last Friday, Orde's barrister, Tony McGleenan, asked that the PSNI's application be heard in closed session. The public, press, Breen, and her lawyers were cleared from the court.

Judge Tom Burgess said the PSNI's application was like "the Grand National course" and he would rule on Tuesday whether it had passed "the first hurdle". If so, Burgess will then set a date for a hearing where the Sunday Tribune can present its arguments. The newspaper's barrister Peter Girvan, instructed by solicitor Joe Rice, said the PSNI's application would be "vigorously opposed".

The PSNI letter demanding Breen's material came from Detective Chief Supt Derek Williamson, who is leading the Massereene investigation. Sunday World journalist Hugh Jordan said: "He seems to have got the wrong end of the stick. Suzanne Breen isn't his enemy. She was simply doing her job. Derek Williamson should wise-up."

According to the editor of the Belfast Telegraph, Martin Lindsay, "Ms Breen is upholding a valued journalistic tradition, where sources of information are regarded as sacrosanct, and deserves support for her stance."

The Daily Mirror's Northern Ireland editor Gerry Millar said: "If this case is lost, it will endanger every journalist seeking to do their job. Society will lose out."

Willie Frazer of IRA victims' group Fair said that although the people he represents suffered at the hands of republican terrorists, he fully supports Breen's stance. "It isn't up to her to do the police's job. The PSNI should get off their backsides and chase terrorists, not harass journalists. Is their intelligence so bad they want journalists to tell them what's happening?"

Writing in Index on Censorship, ex-IRA prisoner and author Anthony McIntyre, said: "Journalists who ask the most difficult questions are those who receive the most hassle from the state and its security apparatus."

Ex-IRA informer Marty McGartland said the Sunday Tribune should be praised, "not treated like criminals", for putting the Real IRA's plans into the public domain.

Last week, Breen wrote of how the UDA had boasted to her in 1993 about murdering Catholic father-of-six, Mickey Edwards, as he slept – yet she had never been contacted by police over that.

Edwards' young children had run into the bedroom, begging him not to die. Last week, Edwards's son Michael contacted the Sunday Tribune to support Breen.

In a moving statement, he said that even if Breen knew the names of those who murdered his father, he didn't expect her to reveal them: "I commend the bravery of Suzanne Breen to interview loyalists at a time when they made no distinction between killing Catholic men or women. It's dangerous enough reporting in the North without unnecessary police actions."