The man handed a driver’s licence belonging to the 52-year-old to a civilian garda staff member at Finglas Garda Station shortly after 7am on Thursday.
Following this development, Gardai issued an appeal for this individual to come forward.
The Sunday World has now learned that the man has since come forward and has been ruled out of the investigation.
It’s not yet known where he discovered the ID card belonging to the tragic mum.
A garda spokesperson said: "Today, Wednesday, May 18, 2022, following the public appeal a male has contacted the investigation team and this witness is currently assisting with An Garda Síochána's investigation.
"An Garda Síochána in Ballymun wish to thank the public for all their assistance so far in this investigation and continue to appeal to any person who may have any information on the murder of Lisa Thompson, and who has not yet contacted the investigation team, to now make urgent contact at Ballymun Garda station at 01 666 4400 or the Garda Confidential Line on 1800 666 111."
A senior source previously said: “What was handed in is an official document, an ID card which had her details on it. Gardaí need to know where this document was found.
“At the moment the person that handed in this document is being treated as a witness not a suspect – gardaí are urging him to come forward.
“Gardaí continue to keep an open mind in relation to this murder, and what happened last Thursday at Finglas Garda Station could be just a bizarre coincidence or something of perhaps much greater significance.”
The source added: “While CCTV has been examined at the garda station, hundreds of hours of CCTV has also been gathered from near the victim’s home in Ballymun.”
It is understood that gardaí are working on the theory that Ms Thompson was murdered in a frenzied knife attack at her home on the weekend of Saturday, May 7, receiving around a dozen fatal stab wounds.
There was no sign of a break-in or a struggle or fight in her property, backing up the theory that Ms Thompson more than likely knew her killer.
The latest twist in the case was announced by gardaí in a statement yesterday morning.
“Gardaí at Ballymun continue to investigate the murder of Lisa Thompson, whose body was discovered on the afternoon of Tuesday, May 10, 2022 at her home in Sandyhill Gardens, Ballymun, Dublin 11,” it said.
“On the morning of Thursday, May 12, 2022 at approximately 7.10am, a male handed a document in the name of the deceased, Lisa Thompson, to a Garda staff member at the front door of Finglas Garda Station and left on foot.
“An Garda Síochána in Ballymun are appealing to this male to make urgent contact with the investigation team at Ballymun Garda Station at 01 666 4400 or the Garda Confidential Line on 1800 666 111.”
Gardaí believe that Ms Thompson may have been in the house for two days before her body was found by neighbours on Tuesday afternoon of last week.
Her children have lived with their father for some time, and were not in the house with her when she was killed.
It was previously revealed that a “recent lifestyle change” in the personal circumstances of the victim is being investigated as a possible motive for her murder.
While Ms Thompson did not abuse illegal drugs, it is understood she had developed an addiction issue with prescription medication which may have brought her into contact with ruthless criminal elements.
Locals in Ballymun who have been left shocked by the murder will gather this Friday at 4.30pm for a candlelit vigil in memory of Ms Thompson at The Axis Centre.