What questions are there for O'Neill about McMonagle?
Michelle O'Neill will face questions on Monday afternoon in the Northern Ireland Assembly regarding how her party dealt with former press officer and now child sex offender Michael McMonagle.
The DUP and SDLP have called for "full transparency" from the Sinn Féin leader at Stormont.
Over the weekend O'Neill admitted "serious omissions" from earlier accounts given by the party about work references provided for McMonagle to his new employer the British Heart Foundation.
The references were given by two former Sinn Féin press officers who have now quit the party.
Here are the key questions facing the first minister.
Why provide references?
Why did two former Sinn Féin press officers provide references for McMonagle which failed to mention he was under police investigation for child sex offences?
O'Neill has said she was "aghast and horrified' by the actions of the two former press officers but so far has not said what explanation they gave for providing the references.
We now know from the British Heart Foundation Sean Mag Uidhir and Caolan McGinley raised no concern about McMonagle's suitability for employment or referenced the ongoing police investigation.
Was it a case of the former press officers' judgement being clouded by friendship and loyalty or was it as some have suggested evidence of a cultural blind spot within Sinn Féin when it comes to such cases.
The party has been criticised in the past over how it dealt with previous republican child sex offenders.
Who knew?
Who all within the party knew about the references and how was the leadership left in the dark?
Sinn Féin has insisted the party leadership was unaware of the references until late last month but it has now admitted a HR manager was informed about them last year by the British Heart Foundation.
O'Neill has described that as a "serious omission" from earlier accounts. She said the manager did not inform the party leadership.
But who is this HR manager how did they not red flag references for McMonagle at the time?
This drip feed of information raises questions as to what else has yet to emerge and it has also damaged the party's credibility in getting to the truth of what happened
Why not inform BHF?
Why did Sinn Féin not alert the British Heart Foundation that McMonagle had been suspended from the party and was under police investigation?
According to Sinn Féin Minister Conor Murphy the party did not want to prejudice the police investigation by informing the charity of McMonagle's arrest.
He also argued that at the time McMonagle was facing accusations and there was no way of knowing if he would ultimately be charged.
But this has been contradicted by chief constable Jon Boutcher who said sharing information with the charity would not have compromised the investigation.
O'Neill will likely stick to the line that she was unaware that McMonagle had taken up employment with the British Heart Foundation.
FM pictured standing close to McMonagle
How can Michelle O'Neill insist she did not see McMonagle at an event at Stormont despite standing just yards from him?
This is a big challenge for the First Minister, convincing the public she didn't see McMonagle despite being photographed close to him in Stormont's Great Hall.
She said she was solely focused on Dáithí Mac Gabhann, and his family at the time and was unaware of McMonagle at the event.
Expect her opponents to seize on this and argue the photographs speak louder than her words.
Had the first minister admitted spotting McMonagle then questions as to why she didn't raise a red flag would follow.
BHF's 'due diligence'
Why did Sinn Féin question the lack of "due diligence" exercised by McMonagle's new employers?
At the time this was a veiled swipe at the British Heart Foundation which the charity said caused it "reputational damage".
Some say it felt like classic deflection at a time when Sinn Féin was under maximum pressure.
The party has since expressed regret for the comments according to the charity and there is a sense both sides now want to move on.
Complaint
Sinn Féin has confirmed McMonagle was also involved in an incident with a female colleague. What happened and was there a complaint made?
According to Sinn Féin McMonagle had made his colleague feel uncomfortable at a non-work related social gathering.
The party said it was resolved by a mutual agreement between them at the time.
This information was released at the weekend just days after BBC News NI asked Sinn Féin if it had received complaints about McMonagle from female colleagues in the party.
The BBC was aware of reports that a complaint was made about McMonagle's behaviour towards a colleague and this statement now appears to confirm this.