A flight attendant was forced to let her bosses examine her Facebook pages and bank accounts in a stoush over what she was up to on sick leave.
The employment court move signals a future where bosses will increasingly demand access to what most workers regard as private details, says employment lawyer Andrew Scott-Howman. He said the development could be seen as creepy and intrusive.
Gina Kensington was sacked by Air New Zealand earlier this year following a dispute over sick leave she took to care for her sister.
She said she did not misuse sick leave, and went to the Employment Relations Authority (ERA) seeking reinstatement.
Air New Zealand responded by demanding to see her Facebook and bank details.
Ms Kensington refused, saying it did not have that information when it dismissed her and that "it is well accepted in New Zealand there are general and legal privacy expectations about people's personal and financial information".
But the ERA ordered she must hand over details for March 8 and 9 this year - saying they would provide "substantially helpful" evidence.
"The explanation for taking sick leave must be tested for veracity," said ERA member Tania Tetitaha.
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Facebook information had been used previously to sack people, but adding bank account data went a step further, Mr Scott-Howman said.
He warned there would be a backlash from workers.
"I don't really know that society has seen this sort of thing previously. But at a time when we think we are behaving privately, or at least within a restricted circle of friends, we are actually effectively on trial."
He said courts always wanted to get "the best evidence".
"And the courts see Facebook as a wonderful asset because all of a sudden not only do we have the potential for pictures and so forth but . . . we can see what time statements were made and pictures were taken."
He said globally, and in New Zealand in relation to the GCSB law changes, people were fighting back against such intrusion.
"Because while this is best evidence . . . doesn't it creep you out a bit? It feels intrusive and just, frankly, wrong."
He said it was a form of spying on staff.
"Sometimes it is actually OK to spy, if you are on my time and you are doing something bad - but the question is where you draw the line."
Mr Scott-Howman said Parliament would be forced to pass laws to stop bosses and the ERA going too far. He said the ERA could simply demand evidence be produced.
The most high-profile Facebook sacking case involves Gisborne man Bruce Taiapa, who applied for a week's unpaid leave in March 2011 to attend a waka ama championship.
He was granted three days, but then took the rest of the week as sick leave, claiming he had an injured leg. He lost his job after his boss saw photos of him on Facebook, taken at the waka ama championships.
The ERA upheld his sacking.
Air New Zealand and Ms Kensington's lawyers declined to comment on her case while it was still before the courts.
A hearing was held last Monday, but the findings are yet to be released.