A report to the Garda Complaints Board into allegations of misconduct by the McBrearty family ran to an unprecedented 1,000 pages, the tribunal was told.
The board appointed Chief Supt John Carey to investigate the complaints, which began in late 1996 and continued over a two-year period.
The tribunal is looking at how the board handled a total of 61 complaints from the extended family.
Brian O'Brien, the deputy chief executive of the board at the time, said that when he met Chief Supt Carey to discuss the case in late 1998, the report on the combined cases ran to 1,006 pages, with an additional 1,500 to 2,000 pages of appendices, plus tapes and photographs.
"I had never seen anything the likes of this before," Mr O'Brien said. "Usually we dealt with individual complaints. Occasionally there might be two or three complaints about the same event or a complainant might have complaints about two or three events that might be related and you might have a fairly big report.
"But nothing of the magnitude of this particular group of complaints and the amount of paper that had been assembled."
Mr O'Brien said that the board had also looked at an additional 10 complaints related to the case, which were made by Billy Flynn, a private investigator hired by Frank McBrearty snr.
A "difference of interpretation" as to what constituted a complaint could explain why eight of the complaints were not forwarded to the board by gardaí in Donegal for nine months, the tribunal heard. The complaints were contained in letters from a solicitor representing the family.
"If he made a complaint about a guard in writing or a solicitor made it on his behalf, then in my view it was a complaint in the letter about the conduct of a guard and should be forwarded to the complaints board. That did not happen," Mr O'Brien said.
Earlier, Conor Maguire SC, for the board, said there was some concern that press reports would give the impression that there was a delay by the board in looking at these complaints, when the delay "was in fact the failure of the gardaí to forward the matters". The board chairman and a senior garda representing the commissioner were briefed on the complaints on November 3rd 1998, Mr O'Brien said.