Patrick Corrigan, (Amnesty Blogs: Belfast and Beyond): The arrest on Tuesday of five people by police investigating the murder of Sunday World journalist Martin O'Hagan in Lurgan seven years ago reminds us that no-one has yet been brought to justice for this crime (sadly, just like so many others in Northern Ireland's recent history).

As Kevin Cooper of the National Union of Journalists (NUJ) noted at the time of his murder, Martin O'Hagan was the only "journalist to be killed in Northern Ireland because he was a journalist and because of his work as a journalist".

Martin was an old-fashioned tabloid journalist for the Sunday World newspaper, which publishes editions in both Northern Ireland and the Republic. It is not read by many in the chattering classes and you won't hear it often cited in the BBC NI's Sunday morning newspaper review. Somehow it still manages to shift nearly 300,000 copies from Ireland's news-stands every weekend. Readers are attracted by a lively mix of sex, celebrity and crime.

Martin O'Hagan specialised in the last of these, although if the stories could combine elements of the first two as well, then all the better. He particulary loved to expose the criminal or otherwise unsavoury exploits of Northern Ireland's paramilitaries. Most likely, this is what ultimately cost him his life, shot down as he walked home from the local pub with his wife Marie, one Friday night in September 2001.

In the June following his murder, Marie and one of her and Martin's daughters came to London to participate in Amnesty International's annual media awards and to hear warm tribute paid to Martin. Marie joined Fergal Keane on stage to present the Special Award for Human Rights Journalism Under Threat to an Eritrean journalist, Milkias Mihretab . It was great to see so many of the country's most illustrious journalists applaud Martin's bravery and back our call for justice: 

"With this special award, we hope to have honoured the memory of Martin O'Hagan, recognised the bravery of Milkias Mihretab and sent a message that journalists everywhere deserve the protection of the societies which they serve." 

The NUJ, of which Martin was an active member, has followed the case closely in the years since his murder and have kept the pressure on the police to produce results when none have been forthcoming. On their website, they continue to document the twists and turns of the case: Who killed Martin O’Hagan?  

It would be fair to say that there have been a lot of suspicions expressed over the years as to the reasons behind the police failure to successfully charge any individuals for the crime. An article (Who did it?) from the NUJ's official magazine the Journalist, eighteen months after the killing, explored some of the claims and counter-claims at that time.

Most prominent (and worrying) of the suspicions is that lack of progress on the case could be attributed to the existence among the killers of a police agent who was now being protected. I have no idea if there is any basis whatsoever to that suspicion, but past experience in Northern Ireland makes it by no means an unrealistic fear. See for instance, NI police colluded with killers, a BBC report from January 2007 on an investigation by the Police Ombudsman linking one particular set of loyalist paramilitary police informants to ten murders.

In December 2006, at the time of the inquest, an angry NUJ Irish Secretary Seamus Dooley called for a police service other than the PSNI to investigate the crime: "We find the approach of the PSNI unacceptable and at this stage the only solution is the involvement of an outside police force."  This has not happened, but a police review of the case subsequently took place and yesterday's arrests reportedly involved the retrospective murder review unit of the PSNI. In a case that has seen arrests before, whether or not this most recent police operation will lead to further progress remains to be seen.

A memorial to Martin O'Hagan was unveiled in Belfast's hallowed Linenhall Library in April of this year. There is another in the Sunday World's Belfast offices. 

Let's hope that his passing is marked not just by plaques but by justice.