A woman with "an extreme interest in death and in harm" live-streamed the killing of a cat four months before murdering a man, a court has heard.
Scarlet Blake, 25, is accused of killing 30-year-old Jorge Martin Carreno after she took to the streets in Oxford to look for a victim as he walked home from a night out in July 2021.
He was found in the River Cherwell, with what looked like a blow to the back of his head.
Oxford Crown Court heard it took two years to work out that Mr Carreno did not die from an accident or suicide, but at the hands of the defendant.
"He died because he encountered the defendant on that night," Alison Morgan KC, prosecuting, told the jury.
"He died because he met a person who had a fixation with violence and with knowing what it would feel like to kill someone."
The prosecutor went on to explain how months before the alleged murder, Blake had livestreamed the killing and dissection of a cat.
Blake, of Crotch Crescent in Oxford, used food and a crate to capture the cat and take it to her home where she killed the animal, the court heard.
"The defendant's actions towards the cat show planning, in particular the purchasing of equipment necessary to do what she wanted to do to this cat, and demonstrated a fixation with what it would feel like to cause harm to others," Ms Morgan said.
In the video, in which the New Order song True Faith plays in the background, Blake tells the cat: "Here we go my little friend. Oh boy, you smell like s***. I can't wait to put through the blender."
The dissection included a "scalpel blade and handle into the cat's eyes", the court heard, before Blake removed its fur and skin and placed the body into a blender.
"This is not simply about killing a defenceless animal. Its relevance to this trial is the defendant's overall demeanour," Ms Morgan added.
"The footage shows her to be someone who had a disturbing interest in what it would be like to harm a living creature. What it would feel like to cause suffering before taking a life away."
Blake "boasted" about the killing with others and "her desire to open up a person like her 'little cat friend'".
The court heard Blake had watched a Netflix documentary called Don't F*** With Cats in which a man kills kittens before filming the murder of a human - with the same New Order song playing in the background.
On Mr Carreno, the prosecutor said "he became separated from friends and perhaps lost and vulnerable".
"She targeted him and took him to Parsons Pleasure, where she killed him, leaving his body to be discovered by others over 24 hours later," Ms Morgan said.
The prosecutor said that during the police investigation detectives built up a picture of her background.
"The prosecution alleges that this defendant had an extreme interest in death and in harm," she told the jury.
"It was an interest that went beyond mere fantasy. She described herself to others as being someone who derived sexual gratification from the thought of violence and the thought of death.
"Videos of her with one of her partners engaging in acts of strangulation, consensually, in a sexualised context.
"She spoke to others about what it would be like to kill someone.
"She looked at imagery and saved it on her devices that showed an interest in ligatures being applied around the neck. She talked about harming herself."
Blake denies murder and the trial was adjourned until Thursday.