For the past two weeks the story of Belfast woman Mairia Cahill has dominated the headlines in Ireland.

Abused and raped by an IRA man in the 1990s when she was just 16, she was then repeatedly interrogated by an IRA kangaroo court investigating her claims. She says she told Gerry Adams what had happened to her at the time and that he did little or nothing to help her.

The details of this, which Cahill revealed in a recent BBC TV program, in media interviews and in a private meeting last week with Taoiseach (Prime Minister) Enda Kenny, have shocked people here.

She described being taken to appear numerous times before the four-person kangaroo court in an apartment in Belfast and being made to face her abuser. She was told that the "court" wanted to read her body language to decide who was telling the truth. She described having to stop the car taking her home after the "court" so that she could throw up on the road.

Also shocking has been the reaction of Sinn Fein when the matter was debated in the Dail (Parliament) last week, showing that the party's primary concern was not sympathy for the victim, but protection for its leader.

Adams accepts that he met Cahill at the time but denies that he discussed the details of what happened with her and says that he advised her – and her grand uncle, the veteran Republican Joe Cahill – that she should report whatever may have happened to the police.

Neither assertion is credible. As Mairia Cahill said last week, she did not meet Adams at the time to talk about the weather. And given the attitude of Sinn Fein to the RUC at the time, the idea that he would tell her to go to the police about a crime by an IRA member is not believable.

For most people here credibility is now a huge problem for Adams. It keeps coming up, whether in relation to the Jean McConville murder, or what he knew about his brother Liam's abuse of his daughter, or on numerous other matters, including his continuing denial that he was ever in the IRA.

In this case, that ludicrous denial is a real problem for him since it means he can't admit that he knew much about the IRA kangaroo court which Mairia Cahill was brought before. So he has to stick with the half-story that no one believes.

The controversy engulfed the media here last week, taking pages and pages in the papers and leading the radio and TV news. That was due in no small part to the extraordinary courage of Mairia Cahill, an articulate woman who is determined to force Sinn Fein to admit the truth of what happened to her.

The whole episode has damaged Sinn Fein badly, as is evident from the most recent opinion polls. It has opened a window into the cruel and arrogant way that the IRA and Sinn Fein operated in the past.

And it has exposed the reality today that Sinn Fein is different from normal political parties in that it is run on Stalinist lines where all its members, whatever their misgivings, have to stick to the script provided by the top brass, or else say nothing. It has shown that the party will dodge and deny, twist the truth and even lie to protect itself.

Above all, the reaction of the party leader, Adams, to the controversy has shown that he just does not get it where the sensitive subject of abuse is concerned.

Mairia Cahill says that at the time he met her he told her that sometimes an abuser is so manipulative that the victim may end up enjoying the abuse. He denies saying this, but his statements last week on the issue were not much better.

The lame expressions of concern he intoned in the Dail and his bumbling efforts to put whatever happened in context were deeply disturbing to people here, including his reference to the IRA members on the kangaroo court as "decent people."

His claim that Mairia Cahill was being used by the other parties in a politically motivated attack on Sinn Fein came across as a way of dodging the issue and as insulting to a brave young woman.

Of course there is a political aspect to this. The other parties are delighted to see Sinn Fein under pressure. But that does not negate the issue and it does not excuse Sinn Fein from being honest about what happened to Mairia Cahill.

Also shocking was the reference by Gerry Adams to Mairia Cahill "self-harming" and the assertion by one of the members of the kangaroo court that the rapist was the kind of exciting, attractive IRA man that any young teenager might fancy. That and other scurrilous stuff circulated on social media by Republican supporters last week was clearly designed to paint a picture of Mairia Cahill as a teenager who was unbalanced and may have encouraged her abuse.

Sinn Fein's defense of Adams and the party last week centered on a couple of important points. The first was an attempt to put the kangaroo court "in context." Sinn Fein says that Nationalist areas in Belfast back then were places where the RUC were not trusted and where the IRA provided community policing for local people, including a "restorative justice" system.

Leaving aside the widespread intimidation by the IRA (with nail-studded baseball bats and kneecappings) that went on to keep everyone in these areas in line, that is partially true. But there is a big flaw in this as an explanation of how Mairia Cahill ended up in front of an IRA kangaroo court.

The RUC may have been "unacceptable" in some Nationalist areas in the 1970s and the 1980s, but Mairia Cahill's abuse and rape happened in 1997 and the kangaroo court she faced was in 1999. By then the Good Friday Agreement had been signed, which included replacing the RUC with the PSNI, the police service now operating in the North. There was far less distrust in or fear of the RUC in the late 1990s.

It's far more likely that the main reason for this kangaroo court was to allow the IRA to keep what had happened under wraps.

Adams claimed in the Dail that those involved in the kangaroo court were "trying to help" Mairia Cahill and were "decent people." But Mairia says that one of them had warned her at the time that if she went to the police the rapist, who the IRA then had under house arrest, would be released and she might "bump into him" on the street.

Another part of the Sinn Fein defense last week was that the members of the kangaroo court and even the rapist had been acquitted by the courts. What they did not explain, however, is why this happened.

The reasons are complicated. First of all, there were lengthy delays on the prosecution side – it did not come to court until earlier this year.

It was decided by the prosecution to take three separate cases, two cases against the abuser for rape and IRA membership and the third against the members of the kangaroo court for IRA membership and other offenses. It was also decided that the first case to be heard would be against the abuser for IRA membership, and that the rape could not be mentioned in this trial.

This was not what Mairia Cahill wanted. In spite of this she was initially willing to give evidence that her abuser and another man had asked her to move guns for the IRA. But the failure of the prosecution to interview this other man, who subsequently turned up in court to support the accused and contradict her, undermined her confidence.

The prosecution felt a conviction was far from certain. So she decided not to proceed. Winning this case had been crucial to the rape case and the case against the kangaroo court members – because the abuser's power to intimidate her and keep her silent came from his position in the IRA.

So faced with this prosecution mess – a failure that is now to be investigated by the Director of Public Prosecutions in the North – Mairia Cahill withdrew from the three cases. But she did not withdraw her allegations against the abuser and the IRA "court. Her frustration and anger at the failure of the court system in the North to get justice for her led to her decision to go public.

Several aspects of this are interesting. Firstly, all this happened in the recent past, not earlier at the height of the Troubles.

It also happened in the period when the sex abuse issue in Irish society, particularly involving the Catholic Church, was being exposed. The TV documentaries on the issue in the late 1990s caused a national outcry and made everyone sensitive to abuse cases and how they should be handled.

Despite this, Mairia Cahill was brought before an IRA kangaroo court in 1999 to "investigate" her abuse claims.

The comparison between Sinn Fein and the Catholic Church – institutions protecting members involved in abuse instead of the victims – was not lost on people here. In particular there was the suggestion that the Mairia Cahill case was far from the only one of its kind and that, like in the church, IRA perpetrators of abuse had been shifted around.

Last week Kenny questioned Gerry Adams in the Dail about how many more cases like this there were, and asked Adams how many IRA men involved in abuse had been shifted to the south. In a pointed reference Kenny mentioned Louth and Donegal and "other places" in the south where IRA abusers from the North might have been moved. In being so specific Kenny seemed to be indicating that he knew more than he was saying.

Other reports last week claimed that a dozen or more cases like that of Mairia Cahill happened, including one in which the IRA abuser was moved to the U.S. where sympathizers, who knew nothing about his behavior, helped him set up a new identity on the basis that he was a freedom fighter on the run. Meanwhile, Mairia Cahill's abuser is reported to be living in London.

None of this reflects well on Sinn Fein or on Adams. The silence last week of the usually vocal women at senior level in the party has been striking. Even Mary Lou McDonald has said little other than to back her leader.

No one is suggesting that Adams is any less disgusted by what happened to Mairia Cahill than any other politician here. But his remarks about her "version" and "other versions" of what happened are concerning.

More than anything, what is clear is that anything that might damage Sinn Fein is to be denied no matter what ongoing damage may be done to victims of abuse by IRA men. As always, the party comes before anything else, including the truth.