The broken window pane slashed the leg of the rubbish truck runner who collected the bag, severing an artery.
The woman has been charged for breaching the Waitakere City Council's waste bylaw by failing to contain the glass.
It's thought to be the first case of its kind and sets a precedent for households around the country.
Sarah Scanlon pleaded guilty at a court appearance on March 26 and will be sentenced on Friday.
The council's solid waste manager Jon Roscoe said she was prosecuted because of the severity of the injury.
"It's a very big concern and we want people to learn from it. We want awareness of it."
Worker Sione Li was cut by the protruding glass when he picked up Scanlon's rubbish bag on Oreil Ave, West Harbour last October. The broken pane severed an artery in his leg, causing significant blood loss.
A council report said Li felt his leg go hot as he lifted the rubbish bag into the truck, and looked down to see a large gash.
A truck driver working with him reported seeing "a mass of blood pouring out of his leg".
The report said Scanlon was remorseful when council officers visited. She said she wanted to get rid of the glass so it wouldn't pose a danger to her children.
She could not be contacted for comment this week.
Li was treated in hospital and was unable to work for some time. He didn't go back to the job after recovering and is believed to have returned to Samoa. The council will ask for him to receive any fine paid.
Charles Smith, compliance manager for Onyx Group Ltd, the council's rubbish collection contractor, said it was important to send a message "that there's a human being picking up the bag and he can get injured".
Smith said a serious injury occurred about once a year as a result of dangerous items in bags.
Regular injuries have prompted waste industry body WasteMINZ to push for a move away from manual bag collections to safer wheelie bin systems.
Chairman Paul Bishop said workers received significant numbers of injuries and were at risk of being hit by traffic.
Wheelie bins were safer because they are emptied mechanically into a truck, but more expensive for councils.
"Bags are still probably the majority in most areas, particularly in small, rural areas," Bishop said. "From WasteMINZ as a group, there is a desire to move to a safer form over time."
Local government law expert, Auckland University associate professor Ken Palmer, said each council's waste bylaws would differ depending on the type of collection, but most would have rules regarding hazardous rubbish.
He said the prosecution was "novel" but seemed fair.
"I'd argue that if this has been a problem then the council has to prosecute someone sooner or later to set a benchmark."
He said it could not be challenged on the basis the householder wasn't aware of the bylaw.
"The law presumes you are aware of these restrictions, ignorance is no excuse."
$20,000 fine for glass in rubbish
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