Mr Brophy was getting ready for work at the Oregon Culinary Institute when he was shot dead in an attack prosecutors say was fuelled by money troubles and a life insurance policy.
In 2011 Brophy penned an essay considering the various techniques and motives for killing a husband and getting away with it, starting the online article: “As a suspense writer, I spend a lot of time thinking about murder and, consequently, about police procedure.”
She lists finances, cheating, anger, falling in love with someone else, and domestic abuse as reasons for murder, and also assesses potential weapons: “Guns - loud, messy, require some skill. If it takes 10 shots for the sucker to die, either you have terrible aim or he’s on drugs. “Knives - really personal and up close. Blood everywhere. Eww.”
Prosecutors were barred from raising the essay during Brophy’s trial but alluded to various of the themes when questioning the killer wife.
Brophy had acquired gun parts in the months before the shooting, including a piece which could obscure what gun a bullet was fired from.
“She had the plan in place,” deputy district attorney Shawn Overstreet told the jury.
“She had the opportunity to carry out this murder. She was the only one who had the motive. “Nancy is the only person who could have committed this crime.”
Brophy claimed the gun parts were bought as she developed her new novel about a woman who slowly acquired a weapon to turn on her abusive husband.
She had been caught on CCTV driving to and from the culinary institute in Portland at the time the murder happened but attempted to brush this off as a “coincidence”.
The murder weapon has never been recovered, and Brophy’s legal team argued the fatal shooting may have happened in a robbery gone wrong.
Brophy, who has been held in custody since her arrest in September 2018, is due to be sentenced on June 13.
She has already indicated an intention to appeal against her conviction.