"Could reasonably be expected"
"... require a judgment to be made by the decision-maker as to whether it is reasonable, as distinct from something that is irrational, absurd or ridiculous, to expect that those who would otherwise supply information of the prescribed kind to the agency would decline to do so if the document in question were disclosed under the Act. It is undesirable to attempt any paraphrase of these words. In particular it is undesirable to consider the operation of the provision in terms of probabilities or possibilities or the like."In the High Court, Hayne J in McKinnon v Secretary, Department of Treasury  HCA45 cautioned against applying a "not irrational, absurd or ridiculous" test in substitution-at 
"... when their Honours said, as they did, that the words required a "judgment to be made by the decision-maker as to whether it is reasonable, as distinct from something that is irrational, absurd or ridiculous," to expect certain consequences, they are not to be understood as having used the latter expression as a paraphrase of the former. Rather, they are to be understood, and have since been understood, as doing no more than drawing an emphatic comparison. To do more would have been, as their Honours correctly said, "to place an unwarranted gloss upon the relatively plain words of the Act".Various other leading cases address the issue in different jurisdictions (see this decision [31-34] for a NSW ADT reference list).
To summarise, a decision maker or the tribunal must be able to conclude on the basis of evidence and as a matter of reason that the claimed possible harm or harms can realistically be expected to occur.
Opinion of an experienced senior police officer not sufficient
In Roy v Commissioner of Police, NSW Police Force  NSWADT 120 Judicial Member Montgomery found there was no overriding public interest against disclosure of the manual used by NSW Police officers as the basis for safe work practices when operating under 'Planned Operations' for LIDAR and/or RADAR use. The manual contains operational information about the location selection and stopping of offending vehicles when using LIDAR and/or RADAR.
Police evidence [35-51] was that if disclosed a reader may be able to circumvent Police systems for detecting speeding vehicles, that members of the public who were aware of 'preclusion zone' and 'selection zones' and distances utilised by Police when determining whether to stop vehicles could engage in dangerous driving by accelerating to higher speeds to avoid being stopped by Police, and that disclosure could be detrimental to Police operations and potentially seriously compromise the safety of Police officers and the general public.
Judicial Member Montgomery decided this was a "risk" but concluded the evidence fell short of harm to identified public interests that 'could reasonably be expected."
60. I note the Appeal Panel comments in Johnston in regard to Senior Sergeant Dorrough. Senior Sergeant Dorrough has extensive experience in regard to speed detection devices. I note his evidence in regard to the differences between the devices and I also note that the Applicant has disputed that evidence. The Applicant has not provided any evidence in support of his assertion that there is no practical difference between different types of speed detection devices. In the circumstances I accept Senior Sergeant Dorrough's evidence on that point.(Update:The Appeal Panel on 23 January allowed an appeal, set aside the Tribunal decision and reinstated the decision to refuse access by consent, after agreement between the parties. In these unusual circumstances the Appeal Panel made these observations-emphasis added:
61. I also accept Senior Sergeant Dorrough's evidence in regard to the Respondent's use of the Procedures Manual.62. However, I am not persuaded that the disclosure of the information could reasonably be expected to have the consequences that the Respondent contends. I accept that some risk exists that the effects outlined might follow from the disclosure.63. I accept that the risk that the procedures may be less effective could be increased if a person endeavouring to evade them has access to the Procedures Manual.64. I also accept that the risk of danger referred to in the section 14 Table (2)(d) includes danger to Police officers conducting these procedures.65 However, I am not persuaded that there is more than a mere risk. I do not accept that it "could reasonably be expected" to lead to those consequences asserted by the Respondent.
9. In the circumstances, the Appeal Panel does not consider it appropriate to issue a substantive decision in relation to the Commissioner's appeal. It notes that the Commissioner vigorously opposed the decision of the Tribunal to grant access to the documents in issue; and presented an arguable case. We observe that in these circumstances the decision of the Tribunal below should not be treated as a precedent in relation to future similar access applications.Concerns about harm not based on rational, underlying factual basis
In McKinnon v Blacktown City Council  NSWADT 44 Judicial Member Molony found there was no overriding public interest against disclosure of a report of an external consultant engaged to conduct an investigation into and report on, allegations of maladministration and misconduct by an employee.
Claims by the agency that disclosure could reasonably be expected to prejudice the supply by staff members of confidential information that facilitates the effective exercise of agency functions was supported by evidence of a staff member
53. Mr Mills' said that he had always given full and frank advice in the course of his work in local government. He said that not to do so would be "unprofessional." He agreed that one should expect a bureaucrat to provide full and frank advice. He said he was not aware of anyone not giving such advice, adding that if he knew some had not given full and frank advice, "I would have to report that." He could not point to a single case where "someone had withheld information for fear of anything."....In an earlier decision Hurst v Wagga Wagga City Council  NSWADT 307 Judicial Member Molony had taken a similar approach-he was not satisfied evidence met the standard to support a refusal of access decision concerning an internal audit report on a conduct complaint made by the applicant concerning two council officers:
56. In the open affidavit Mr Mills expressed the opinion that disclosure of the report would impede the ability of the Agency to obtain and rely on such information in the future. He explained that he considered it "reasonable to assume that other council officers will be reluctant to report misconduct or inappropriate behaviour in future, for fear of reprisal." In my view the cross-examination of Mr Mills demonstrated that he had no reasonable basis for holding this opinion, and that the assumption was not reasonably held. He had no experience of anyone withholding information that they were duty bound to disclose, whether for fear of reprisal or otherwise.
57. Additionally, Mr Mills gave evidence that all the investigations he had been associated with had been treated as and kept confidential. As a result he has no experience of investigations where confidentiality has not been maintained. A consequence is that, in the formation of his opinion, he did so from the basis of having no experience he could contrast with the confidential treatment he was used to.58. His concern that staff will be reluctant to provide information in the future, therefore, is not based on experience or informed by fears voiced by him or other council staff. It is not based on a rational, underlying factual basis. Indeed his evidence in cross-examination points to conclusion that he has no reasonable or rational basis for the opinion he expressed. The assumption he relies on takes a very dim poor of the integrity of council staff, which is entirely at odds with his own experience. I do not accept his opinion.....
61. In her statement Ms McCormack said that she has worked with three General Managers at the agency in Code of Conduct investigations. She has acquired a detailed knowledge of the Council's policies, procedures and practices relating to such investigations. She said that:
- Staff members who are the subject of complaints are given access to the information in the complaint to ensure procedural fairness.
- Nothing in the Code of Conduct authorises a complainant to have access to staff responses.
- Complainants are not given access to staff responses.
- The Council's practice in restricting Code of Conduct information is consistent with s10A of the LGA.
- It is the practice of Council that statements made in response to Code of Conduct complaints are confidential.62. Ms McCormack said that in her experience -" ... the effectiveness of Code of conduct investigations into Council staff matters relies on information that it provided to, or produced by, the Council only being made available to Council officers involved in the investigation process....protection of information in this way promotes and environment of trust and confidence in which the complainant, staff and witnesses can provide candid information to the general manager, and the general manager can determine a complaint, without fear of the potential embarrassment or reputational or other harm that may result from the release of the information in other circumstances to other people."63. These expressions of opinion by Ms McCormack are based on her experience in an environment where, as a matter of practice, staff responses to Code of Conduct investigations have been kept confidential. She does not depose to having any experience of code of conduct investigations where confidentiality was not maintained.64. Given her experience, it is difficult to understand on what basis she can reasonably claim that the effectiveness of code of conduct investigations "relies" on that confidentiality. Her evidence does not disclose any other basis for the formation of her opinion, aside from the fact the confidentiality has been maintained in all the investigations she has been involved in. In those circumstances it is difficult to give her opinion as to the consequences of disclosure any weight, as they are assertions based on her experience, gained in investigations where confidentiality was maintained as a matter of practice.65. Her evidence does not identify any basis for a comparison between investigations where confidentiality has been maintained, and those where it has not. It does not disclose a rational or underlying factual basis for the conclusion that, if information provided by staff were disclosed, it could reasonably be expected that staff would be unlikely to co-operate with investigative processes. This strikes me as taking a very dim view of the integrity of council staff, and of their willingness to ensure that the processes they manage are conducted efficiently, effectively and honestly. I conclude that Ms McCormack opinion is based on limited experience and involves considerable speculation. I do not accept that it is reasonably or rationally held.
37. The usual practice of the Commissioner, as explained by Detective Senior Constable Ammon, when actioning a reported alleged offence by a member of the public, is to interview the relevant parties and then determine what, if any, action is to be taken. In conducting those interviews, police obtain and record the personal details of each person interviewed. However, these details are kept confidential, subject to charges being laid. Where no charges are laid, it is the usual practice of police to keep any information that is obtained, including personal details, confidential. Detective Senior Constable Ammon explained that maintaining confidentiality in such circumstances is extremely important to the Commissioner's policing functions. He expressed this to be 'the bread and butter of policing.' That is:'If police did not keep information from members of the public confidential, our justice system wouldn't work. People wouldn't want to supply statements to the police and we wouldn't be able to investigate and prosecute offences.'38. Detective Senior Constable Ammon also explained that the Commissioner's 'Customer Service Charter' advises members of the public, who report matters to police, can be assured of confidentiality. Without that assurance and a trust in that assurance being maintained, the Commissioner and his officers would not be able to fulfil their functions.39. On the basis of the evidence I am also satisfied that the information in dispute was obtained in confidence and if disclosed could reasonably be expected to prejudice the supply of confidential information of this kind which facilitates the effective exercise of the Commissioner's functions.