The Disclosures Tribunal has heard that Garda Keith Harrison checked his partner's details on the Pulse system repeatedly because he believed they were under garda surveillance.
Garda Harrison faced a disciplinary action in 2012 for not having a valid reason for accessing the details.
His checks arose following a garda investigation into issues highlighted in an anonymous letter sent to gardaí alleging concerns for his partner's children.
At the time, Garda Harrison's relationship with Marissa Simms had broken up and she was back together with her ex-husband.
Garda Harrison says he checked Pulse because he believed they were under garda surveillance.
He disputes the figure of checking "over 30" times and puts the number of checks at 22 between 2007 and 2012.
This section of the tribunal, chaired by Supreme Court Judge Peter Charleton, is investigating contacts between the child and family agency Tusla and gardaí about Garda Harrison.
The tribunal is investigating whether the social work interactions were influenced by senior gardaí.
The first witness, retired chief superintendent James Sheridan, gave evidence that he told Garda Harrison the inappropriate Pulse access was unacceptable and Garda Harrison said it would stop.
The tribunal heard that in 2011, Garda Harrison transferred to Buncrana station from Athlone to be near his partner.
He did not disclose at the time that he was in a relationship with the sister of a man facing manslaughter charges for the death of a local garda.
In 2009, Marissa Simms' brother Martin McDermott had been driving at speed when he crashed into a car, killing Garda Gary McLoughlin.
Garda McLoughlin had been serving in Buncrana station in the same unit that Garda Harrison later joined.
Some gardaí later refused to serve alongside Garda Harrison in Buncrana.
Mr Sheridan, who was in charge of the Donegal division at the time, met with Garda Harrison and Superintendent Kevin English to discuss the issue in May 2011.
Mr Sheridan said the meeting was calm, however, the tribunal heard that Garda Harrison will say that chief supt Sheridan was angry that he had not disclosed the relationship.
Mr Sheridan said it was incumbent on Garda Harrison to disclose the relationship and his recollection was that Garda Harrison fully accepted that he could not continue in Buncrana.
He said that Garda Harrison pleaded to be transferred elsewhere in Donegal.
Mr Sheridan agreed to transfer him to Donegal Town.
The tribunal also heard that Garda Harrison was previously refused transfers to several other divisions, including Limerick and Laois/Offaly
His lawyer, Mark Harty SC, suggested that this was unusual and that there appeared to be personal issues with Garda Harrison. Mr Sheridan agreed.
In October 2011, Garda Harrison was refused a transfer from Donegal town to Letterkenny. Mr Sheridan said it was too soon after McDermott's manslaughter conviction.
Mr Sheridan said Garda McLoughlin's death would never be forgotten and he would always be associated with Buncrana.
He said he was trying to be fair and there was no malice in his decision to transfer Garda Harrison to Donegal Town.
Mr Harty said neither Garda Harrison nor his partner had any connection to the death.
Mr Sheridan denied that he maliciously transferred Garda Harrison.
The tribunal heard this afternoon that there was anger and annoyance in Buncrana Garda Station when it emerged that Garda Harrison was in a relationship with the sister of a man charged with the manslaughter of another garda.
Retired sergeant Daniel Devlin said that the news came out of the blue in May 2011, a few weeks before the trial, and emotions were "taut".
He was in charge of the unit where Garda Harrison served and it was the same unit where Garda McLoughlin was stationed at the time of his death.
Mr Devlin said he was told that some gardaí would find it very difficult to serve alongside Garda Harrison.
Garda Harrison went on leave awaiting transfer but on the night he left, he addressed the unit and apologised for not disclosing the relationship earlier.
Mr Harrison and his partner will give evidence next week.
In November, the tribunal will return to allegations made by Sergeant Maurice McCabe.