Cameron Staples left his four-month old baby boy alone to buy booze, then got drunk and shook him.
Flynn died in hospital four days later.
His bereft mother, Robyn Hall, says her precious baby wasn't given a chance at life.
Staples, 35, has pleaded guilty to child homicide at the couple's Kilsyth home, in Melbourne's east, last May.
Staples left Flynn alone to buy bourbon and coke, drank seven or eight cans and inflicted horrendous injuries on his defenceless son.
Ms Hall had gone out and when she returned, Staples lied.
He claimed the baby fell from the change table as he ducked out of the room to put a nappy in the bin.
Ms Hall found Flynn moaning with his jaw clenched tight and bruised.
His brain was swollen and he died from injuries associated with forceful shaking and hitting a hard surface.
Staples then changed his story, saying he'd been drinking, was too rough with the baby and put him "pretty hard" down on the floor.
Seventeen months later, Ms Hall says the pain and anger is "like a fire burning inside of me".
"I devoted my life to Flynny and his father," she said in a statement read to Victoria's Supreme Court on Tuesday by prosecutor Neill Hutton.
"And then it was all gone. My whole world shattered that night.
"I don't want to be here without Flynny, I don't have a role anymore. What's the point?"
She couldn't understand how Staples could be so selfish and "hurt our perfect baby boy".
"Flynny didn't even get a chance at life."
Staples has been diagnosed with a personality disorder while in custody awaiting sentence.
"He acknowledges the many victims in this incident, including himself," his lawyer Cynthia Lynch said, adding Staples too had lost his son.
He blamed what happened on the alcohol, and had written an apology to Ms Hall and her family.
Flynn's grandpa, Tony Hall, said he cried nearly every day.
"The site of his coffin, which was the length of my arm, is etched forever in my memory," Mr Hall told the court through tears.
His wife, Gill, said "there is no place to escape from the loss of Flynn".
Justice Paul Coghlan will sentence Staples next Thursday.