A mother feared for the safety of her baby at the hands of his father shortly before his death, a court has heard.
Seven-month-old Oskar Kennedy-Jobey was pronounced dead in hospital after Kane Kennedy called paramedics to their home in Morecambe last October.
Appearing at Preston Crown Court, Mr Kennedy, 20, denies manslaughter and murder and blames Oskar's mother Tia Jobey, 19.
She admitted causing or allowing Oskar's death.
Jurors at Mr Kennedy's trial were read messages sent between the pair before Oskar's death in which Ms Jobey claims the father was abusing the boy.
'Throw like toy'
In one of the Facebook messages, she wrote: "I'm trying to make sure Oskar is happy and safe and while you are addicted to weed and violent and abusive he's not safe at all.
"You throw him around like a toy, suffocate him, stick your finger down his ... throat. And he's always in the middle of our arguments and fights."
The jury was told Mr Kennedy and Ms Jobey had a turbulent relationship and would often argue about his cannabis use and immaturity.
Neighbours heard them arguing loudly and could smell cannabis coming from the flat on a regular basis, the court heard.
In a police interview, Mr Kennedy said he fell asleep with the baby under his arm and woke at about 08:45 BST on 1 October to find him not breathing.
Police and paramedics attended the flat on Balmoral Road and found Oskar unresponsive but still warm.
The infant was pronounced dead an hour later at Lancaster Royal Infirmary.
A post-mortem examination revealed a catalogue of non-accidental injuries to Oskar's face, mouth and genitals and concluded he died from smothering.
Home Office pathologist Alison Armour concluded Oskar's injuries "negated the possibility" of overlaying as a cause of death, the court heard.
Prosecuting, Paul Reid QC said "it is plain" Mr Kennedy grabbed his son's genitals then, "possibly in an attempt to silence the baby's inevitable cries of pain, pushed his fingers into Oskar's mouth thereby deliberately smothering the baby".
The prosecutor said: "Not only was really serious harm entirely foreseeable from such behaviour, the prosecution say Kennedy must have intended it."
The trial, expected to last one week, continues.