Work Christmas parties by definition blur the lines between work and social life, and in so doing, present the opportunity for a broader gamut of behaviours to surface. Add in a little alcohol, a novel setting, a few extra characters, and the scene has been set for questionable conduct to emerge. If complaints are made, offending public servants may find themselves facing disciplinary processes that will drag well into the new year. The ultimate Christmas hangover.

Most public servants get the message: treat work social functions like work. If you wouldn't do it in the office, don't do it at the Christmas party. Misconduct at these events can legitimately be the subject of workplace discipline under sections 13 and 15 of the Public Service Act 1999, because it is sufficiently "connected" with Australian Public Service employment.

But what about other out-of-work gatherings where work colleagues are involved? (Think for example, the Christmas after-party, or privately-organised weekend events). To what extent can and should HR be concerned with the conduct of APS employees at these events?

Where the employer has exercised some control or endorsement over the person's off-duty behaviour, the premises where the conduct occurred, or supplied the equipment to allow the offending conduct to occur (such as laptops or mobile phones), then the required "connection" with employment might be established.

But courts have repeatedly warned that public servants are entitled to a private life, and any employer intervention in this must be "carefully contained and fully justified".

Since the case of Rose v Telstra, it is well-settled law that out-of-hours conduct which, viewed objectively, meets any of these three criteria, might justify employer intervention (including by dismissal from employment):

Applying this test to any particular situation is the tricky part. In the case of Mr Rose, his out-of-hours fight in a public bar whilst on a work trip, did not meet any of the above criteria, not least because he was not readily identifiable as a Telstra employee, and so it was difficult to see how Telstra's interests were affected by the brawling.

But there are situations where out of hours conduct can attract the legitimate attention of APS employers.

For example, some out-of-hours romances may put an APS employee in a conflict of interest situation at work. So, an SES officer who has a (consensual) liaison with a direct report in her private life, but who does not disclose or manage this conflict of interest at work, may well offend all of the three Rose v Telstra criteria above because of perceptions of "favouritism" arising in the office at senior levels. Employers can't stop employees from forming romantic relationships; but they can legitimately require employees to manage this properly in the office.

Private sexual harassment between colleagues, that spills over to have "significant and adverse effects in the workplace", might also be the legitimate subject of employee direction and discipline. In McManus v Scott-Charlton it was held that AusAID employee Mr McManus' out of hours conduct in repeatedly calling a colleague, and his ongoing proximity to her at work, caused both her and her colleagues apprehension at work. This affected the workplace, and in doing so, could be said to have damaged AusAID's interests.

What about private life conduct that might be thought to affect the employer's reputation, by association? The range of such conduct is infinite - though the usual suspects include drug and alcohol use, sexual misconduct, domestic violence and criminal offences, and increasingly, social media comments critical of the agency.

Applying the Rose v Telstra test, private conduct which is likely to cause serious damage to the employment relationship, or the employer's interest, can legitimately ground both disciplinary decisions and a fair dismissal. However, two things need to be said about this. First, case law to date suggests that potential reputation damage is not enough; the employer must have evidence of reputational harm, not mere concern or risk that this might arise in future. Secondly, should employers prefer to rely on the third limb of the Rose v Telstra test to assert that such acts are "incompatible" with the employee's duties, HR managers would be well advised to ignore any moral repugnance, and focus on the connection between the act and the employment, and the effect on the performance of work or the employer's business.

On this assessment, private drug use say, by an APS employee of any classification that interferes with the performance of their duties would be an act incompatible with the employee's duties as an employee, and might justify discipline and dismissal. Private drug use by an APS employee that does not interfere with the performance of their duties is not of legitimate concern to the employer, unless that drug use causes reputational or other damage to the employer. For example, if an employee's illicit drug use becomes public knowledge and the employee in question works in a law enforcement agency, then this is likely to be problematic. Further, the more senior the employee the more likely their private conduct being exposed will cause reputational damage (for example, a deputy secretary as opposed to an APS 4 employee).

Some public servants may still be reeling from this year's High Court decision in Comcare v Banerji. Perhaps they should not. Michaela Banerji was terminated from her APS 6 employment as a communications officer for making anonymous tweets in her spare time, critical of the Department of Immigration and Citizenship policy on refuges. But Banerji was a workers' compensation case that raised constitutional law issues, not an unfair dismissal case. Banerji effectively decided that section 13(11) of the Public Service Act (a.k.a. the Code of Conduct) that requires a public servant to uphold the integrity and reputation of the agency and APS "at all times", did not offend the implied constitutional freedom of political communications. However, if the matter had run as an unfair dismissal case, applying the criteria set out by Justice Edelman in that decision, the department may well have had a much more difficult time defending the dismissal.

Merry Christmas.