The Crown alleges Milner killed Mr Nisbet, most probably by slipping up to 50 crushed tablets of anti-histamine drug and sedative Phenergan into his food, then smothering him with a pillow.
Despite concerns raised by the first two police officers on the scene of his death, where they raised suspicions that Milner's grief "appeared to be acting", police treated it as suicide.
A homicide investigation was launched two years later when a coroner raised questions over the death.
Milner, 50, denies murdering her second husband, and that she had tried but failed to kill him by poisoning him twice on the same day a month earlier.
The Crown alleges she was motivated by a fatal desire to cash in the $250,000 life insurance policy and had plotted and planned it for months.
Milner wasn't interviewed by police until one week after her husband's death on May 4, 2009.
She gave a statement to detective Richard Prosser on May 12 where she said Mr Nisbet must have taken an overdose of Phenergan tablets.
The office worker directed police to where packets of the sedative and anti-histamine drug were located in the house in Halswell, Christchurch.
Police officers found packets of the drug in the top drawer of the bedside table beside where Mr Nisbet's body was found.
But the first officer on the scene said when Milner directed him to another stash of the drug in the kitchen that morning, he couldn't find any.
A week later, when Mr Prosser called by, he found them exactly where Milner said they would be.
The contradiction emerged on day three of the High Court murder trial in Christchurch.
Mr Prosser said he had been tasked with looking into the sudden death and preparing a report for the coroner.
Milner was not treated as a suspect and gave evidence of her own volition.
During an 8-page statement to Mr Prosser on May 11, she told him she thought Mr Nisbet had died of an "overdose of tablets".
The court has heard from more than a dozen former colleagues at Christchurch grounds maintenance firm GSL who gave testimony that Milner would speak about how unhappy she was in her marriage and that she wanted to "get rid of him", asking if rat poison would work.
They nicknamed her the "Black Widow".
But in her first statement - she gave another one on January 30, 2010 to clarify some matters arising from police inquiries - she told how they had enjoyed a normal marriage and they were "very happy"together.
The day before his death, they had enjoyed a "lovely" Sunday, the statement said. They had watched crime comedy-drama Bones on TV, before Mr Nisbet retired to bed, and she made his lunch for the next day.
Milner, a diabetes sufferer got up at 2am to eat toast and drink milo and boost her sugar levels, she said, before going back to sleep on the couch.
She woke at 5.45am and said she went to rouse her husband, who was due to get up for work.
In her statement she said: "I knew he was dead straight away."
The first two police officers on the scene - constables Christopher Barker and Grant Cowan - raised concerns between each other, and their superiors, over her reaction.
"It was very unusual. It appeared to be acting," Mr Barker said today under cross-examination.
The trial, before Justice David Gendall, continues.
