Given Ireland's notoriously weak laws on white-collar crime, it was probably inevitable that the Director of Public Prosecutions would withdraw corruption charges against five defendants, including a serving councillor and three former councillors, when the chief witness against them proved unable to continue giving his evidence.

With no other former councillors facing charges for taking payments from developers to have land zoned in the early 1990s, the upshot is that only Frank Dunlop himself – the "bagman" for many of these disreputable transactions – has served a prison sentence. Those who took bribes, as the Mahon tribunal found, have not.

For anyone who saw what was going on in Dublin County Council’s makeshift council chamber on Upper O’Connell Street – as I did – the outcome confirms the culture of impunity. The building is now gone, but we are still living with the consequences of decisions made at the behest of developers.

As I wrote after the tribunal published its final report in March 2012, some people are living in floodplains as a result, while others have no option but to get into their cars to travel to a shopping centre because the one that was planned nearer wasn’t built, because councillors persistently ignored the advice they got from professional planners.

"Corrupt and bad planning decisions have a significant impact upon people's lives," said Jerry Barnes, of the Royal Town Planning Institute (Southern Ireland). And he cited as a prime example the 1991 rezoning of Quarryvale – tainted by widespread bribery – as a "town centre" for the Lucan/Clondalkin agglomeration in west Dublin. It didn't matter that an actual town centre had been planned for 20 years in a central location to serve the area. What happened was that the town centre was relocated to the northeastern extremity of this burgeoning "new town", at the edge of the M50 – because that's where developer Owen O'Callaghan wanted to build it.

Those who championed the radical change of plan, notably the late Liam Lawlor and former Fianna Fáil councillor Colm McGrath, were paid handsomely for their support by Dunlop from his ample "war chest". Many other councillors also received smaller sums for voting for the Cork-based developer's daring scheme.

Just last month, the Liffey Valley shopping centre at Quarryvale was consolidated by a Bord Pleanála decision to grant permission for a Tesco "anchor store" with 551 parking spaces – on the basis that the 180-acre site had been zoned for "town centre" use. Senior planning inspector Robert Ryan had recommended a refusal.

As he noted, Liffey Valley “represents an almost classic ‘American style’ shopping mall very much dependent on the private car and relatively remote from existing long-established urban centres”. Indeed, even South Dublin County Council’s local area plan describes it as “off-centre” in relation to the communities it is meant to serve.

The blame for this state of affairs lies with the councillors who took money from Dunlop and voted to discard the original plan, in favour of adopting the new one put forward by a developer. The decision they made in 1991, setting the stage for this “off-centre” shopping mall, was undoubtedly the most corrupt in the history of Irish planning.

It wasn't only county councillors who were shaking down developers for money; the corruption reached into the corridors of power in Leinster House. The original Quarryvale developer, Tom Gilmartin, faced what the tribunal called an "undeniably corrupt" demand for £5 million after meeting then taoiseach Charles Haughey and ministers.

As recounted in the tribunal’s final report, the shocked Sligo-born developer told the still unidentified individual who demanded that this sum be lodged in an Isle of Man bank account that he made “the Mafia look like monks” and was then warned by him that he could “wind up in the Liffey for that statement”. In concrete shoes, presumably. “The heart of the Mahon findings is that the system was manipulated to serve certain private interests rather than the common good,” as Barnes said. As a result, there had been “a vast and damaging overzoning of lands throughout the country, much of it in the wrong location” – and generations will be left living with the consequences.