A number of witnesses in the Eastman inquiry have been asked to explain why they should not be criticised in the final report.
Seven notices were posted last month, with the deadline for written responses to close on Wednesday.
The inquiry will reconvene to hear arguments on Monday.
The ACT Inquiries Act requires the board to notify participants via 26A notices if it intends to include an ''adverse'' comment about them in the final report.
The board must also give ''the entity a copy of the proposed comment''.
The recipient of the notice then has 14 days to lodge a written response.
A copy of the response will then be included in the board’s final inquiry report.
Assistant Australian Federal Police Commissioner Colin Winchester was shot twice in the head in Deakin in January 1989.
David Harold Eastman, who has served 18 years of a life sentence, was convicted by a jury of the murder in 1995.
He has always maintained his innocence.
In 2012, judge Shane Marshall ordered an inquiry into the conviction after he was satisfied there was "fresh doubt or question" about Eastman's guilt.
He ordered the inquiry based on 19 wide-ranging grounds, including the conduct of the prosecution and investigating police.
It is understood Victorian forensic scientist Robert Barnes, whose work helped convict Eastman at trial, and the Australian Federal Police were among those to receive a notice.
Mr Barnes is thought to have run out of funds for his legal team and it is unclear how he will respond.
His analysis of gunshot residue provided a critical link between Eastman and the murder scene, and helped eventually secure the conviction.
Mr Barnes’ work on the case was put under the microscope during the recent public hearings, leading to allegations he overstated the strength of the evidence and allowed "unacceptable confusion" in the labelling of exhibits.
Wednesday is also the cut-off date for final written submission from all parties.
Final verbal submissions will also start next week.
The inquiry heard evidence from its final witness in April, drawing to a close five months of public hearings.
Once verbal arguments are finished, the inquiry head, Acting Justice Brian Martin, will complete and deliver his final report.