The non-jury trial was adjourned in December last year to allow the property magnate's lawyers view CCTV footage that had not previously been disclosed to the defence.
The case resumed before the three-judge court today, with witnesses in the Witness Protection Programme (WPP) expected to continue giving their evidence in the coming days.
Mr Mansfield Jnr (53), of Tasaggart House, Garters Lane, Saggart, Co Dublin, has pleaded not guilty to conspiring with one or more persons to falsely imprison Martin Byrne on a date unknown between January 1, 2015 and June 30, 2015, both dates inclusive.
He also denies attempting to pervert the course of justice by directing Patrick Byrne to destroy recorded CCTV footage, with the alleged intention of perverting the course of public justice in relation to the false imprisonment of Martin Byrne (53) at Finnstown House Hotel, Newcastle Road, Lucan, Co Dublin between June 9, 2015 and June 12, 2015.
Last year, Martin Byrne testified that Mr Mansfield Jnr was "a couple of feet away" when he was taken prisoner by the gang of men, which included former INLA man Dessie O'Hare and former Republican paramilitary Declan 'Whacker' Duffy, after a meeting at a warehouse at Keatings Park in west Dublin. In his evidence, Mr Byrne said that he believed Mr Mansfield Jnr had set him up.
Martin Byrne is now in the WPP along with his wife Lisa Byrne and their son Brandon Byrne (24).
This morning, defence counsel Tony McGillicuddy BL told the three-judge court that they had received replies to all disclosure requests but he was formally challenging redactions which were made.
Shane Costelloe SC, who appeared on behalf of the Director of Public Prosecutions (DPP), said he had an answer to each of the redaction requests and proceeded to address each of them individually.
The trial was originally adjourned last November when Mr Costelloe submitted that gardaí had only become aware that a significant proportion of CCTV footage retained on a hard-drive had never been disclosed to the State. The defence said it amounted to 12 days of CCTV footage and the case should not proceed until they had an opportunity to view the material.
When the trial recommenced before the non-jury court in December, defence counsel Bernard Condon SC said there had been delays in serving the defence with the newly disclosed CCTV footage and he asked for a further adjournment to view the material, which was acceded to.
Furthermore, Mr Condon said "a very significant piece" of CCTV footage was only served on the defence despite the cross-examination of Martin Byrne having concluded. The court previously ruled that Mr Condon would be given another opportunity to put further questions to Martin Byrne when he is brought back to the jurisdiction this week.
The trial continues before Mr Justice Alexander Owens presiding, sitting with Judge Sinead Ni Chulachain and Judge James Faughnan.
Mr Justice Owens previously said he did not expect the trial to finish before the court breaks at the end of this month. Whatever evidence remains to be heard, the judge said, will be adjourned to when the court returns following the summer break.