Summarize this content to 2000 words in 6 paragraphs Why he did it is still unknown, given Rebelo maintains his innocence, but on Monday, ahead of being sentenced, prosecutor Brett Tooker put forward some theories to Justice Bruno Fiannaca in an attempt to assist him in finding a suitable term of imprisonment.He told the court that Rebelo’s main motivation for killing his mum was to prove to his then-girlfriend that he was financially successful and that he could contribute to the relationship.Rebelo and Piscopo often appeared in photographs looking glamorous.Credit: InstagramRebelo was dating an Instagram model, Grace Piscopo, when he murdered his mother in 2020. At that time, Piscopo was making six-figure sums modelling clothing and accessories via her social media profile, a role that become a full-time business for her.In contrast, Rebelo had dropped out of university and was driving delivery trucks for Coles before becoming a stay-at-home dad to the couple’s young son and helping Piscopo with administrative errands.He was also attempting – and failing – to become a successful crypto-trader and promised Piscopo, Tooker claims, that he would be coming into a $500,000 windfall around the time he “hatched a plan” to kill his mother and draw down on three life insurance policies.“His motive for killing his mother was a financial one,” Tooker told the court on Monday.Piscopo arrives at court to give evidence in Rebelo’s defence.Credit: 9 News Perth“Often murder is committed for passion or jealousy or other things. Less common is a person who kills a person for financial reasons.“In my submission, that was his motive … it was a calculated and cold-blooded killing.”Rebelo was not suffering from any psychological conditions, the court was told. The 28-year-old declined an evaluation from a doctor, which usually offers the court some information that reveals what motivated a person to commit such a crime.Instead, Tooker said it was about “the pressure he felt”.“He made promises to Ms Piscopo and wanted to fulfil those promises in relation to the money he was expecting,” he said.Tooker added that Rebelo’s motive was also to get the money to clear debts he and Piscopo had accumulated in living beyond their means with a lavish lifestyle, including an expensive rental property and finance for a costly car.He also wanted equity to continue crypto-trading, Tooker said.On Monday, the court heard Rebelo’s twin sister, Monique, had submitted a victim impact statement to the court, speaking of “the very close bond” she had with her mum and the “great loss” she has suffered since her death.LoadingColleen’s sister, Leonie Randalls, also submitted a statement saying it was a “tragic case because she gave so much to her children and that her life was taken by her own son.”A cohort of Colleen’s family listened to Monday’s proceedings via an audio link and Rebelo’s father attended the court in person.He will be sentenced on Tuesday at 11am.