Robert and Cheryl Adamson were caring people who thought they were coming to the aid of a neighbour before they were brutally stabbed to death in their home.
Thomas James Hemming, 21, of Murrumbeena was sentenced to 32 years jail on Friday over the February murders and will have to serve a minimum 27 years before becoming eligible for parole.
Justice Betty King described the Melbourne double murders, to which Hemming pleaded guilty, as "horrific" and "entirely inexplicable and incomprehensible to anyone involved" during sentencing in the Victorian Supreme Court.
"It's bizarre and undoubtedly incredibly distressing to the family and friends of the victims that they were killed for no reason other than your fantasies and desires to kill any person," she said.
"These were two decent, caring, helpful people who came to the aid of a neighbour only to be brutally murdered."
Hemming, who has Asperger syndrome, had been drinking before going to the Adamsons' Murrumbeena home, near where he lived with his own family.
About 6am on February 19 this year Hemming knocked on their door and asked to use the phone.
They invited him into the living room where Hemming repeatedly stabbed Mr Adamson, 65, in the back.
His 60-year-old wife came to his aid with a broom, hitting Hemming with it.
"Consequently you turned your attention to her and stabbed her multiple times," Justice King said.
"Cheryl Adamson died protecting her husband, and then herself."
Justice King said it took Hemming 547 questions in a police interview before he admitted what he had done.
She said his lack of remorse made him an "exceedingly poor prospect of rehabilitation".
"You remain incapable of feeling any empathy, sorrow or regret for your fellow human beings," she said.
"You knew what you did was wrong but there's nothing to indicate you wouldn't do it again."
Justice King said the murders had, for many people, shattered the illusion that people were safe in their homes.
She said the Adamsons' son and daughter had experienced anger, grief, bewilderment and frustration that their parents had been killed in their own home.
"Above all they feel loss," she said.
"It was unfortunate that their son was the person who found the bodies and undoubtedly that will be difficult to ever erase."
Hemming has already spent 244 days in custody.