A father who smothered his seven-month-old son to death after he inflicted "frankly obscene" injuries to the child has been jailed for life.
Kane Kennedy, 20, forcibly got hold of Oskar Jobey-Kennedy's testicles by either gripping, pinching or twisting them.
He went on to push his fingers down the throat of the defenceless baby before finally placing his hand over Oskar's mouth at the family home in Morecambe, Lancashire.
On Thursday, Kennedy moved his hand over his own mouth in shock at Preston Crown Court as he was told he must serve a minimum of 18 years in detention before he can be considered for parole.
The regular cannabis smoker was said to have been "bad-tempered" when he could not get hold of the drug and argued regularly with Oskar's mother, Tia Jobey, 19.
Prior to Oskar's death on October 1 last year, Jobey sent text messages to Kennedy in which she confronted him about previously pushing his fingers down Oskar's throat and putting his hand over his mouth.
Sentencing, Mr Justice Davis told the defendant: "Oskar was seven months old when he was killed by you. Obviously he depended on those who had charge of his care to protect him and in his case both of those with immediate responsibility failed him.
"His mother knew that he was at serious risk and she did nothing adequate to protect him.
"Her culpability pales into insignificance compared to you. You are the one, on the jury's verdict, that killed that tiny baby.
"I am quite satisfied that what you did in the early hours of October 1 2015 was not a single isolated act ... you had deliberately ill-treated that child in the days and weeks prior to his death."
Although the judge accepted that Kennedy did not intend to kill his son, he questioned whether his actions were "out of some perverse kind of fun".
He added: "It was a dreadful thing to do to a seven-month-old."
The judge told Kennedy he was not someone who was in a "desperate situation" and had a "well supported" family background.
Michael Hayton QC, defending Kennedy, said that on the evidence heard both Kennedy and Jobey had "in large part" not been doing a bad job in bringing up Oskar and this was not a case of a "campaign" of abuse inflicted on the child.
Kennedy, who maintains his innocence and pointed the finger of blame at Jobey when giving evidence, was stunned as sentence was passed and shook his head as he was led from the dock.
Last week, Kennedy, formerly of Harewood Avenue, Heysham, was convicted by a jury of murder. He had denied murder and manslaughter.
Following conviction, detectives investigating the case described the injuries inflicted on Oskar as "frankly obscene".
Jobey, 19, of Balmoral Road, Morecambe, pleaded guilty at an earlier hearing to causing or allowing the death of a child and was sentenced last week to 30 months in a young offender institution.
The court heard Jobey and Kennedy started arguing two months before Oskar's death over Kennedy's use of cannabis.
Jobey told police Kennedy would be "stressy" when he could not smoke cannabis and said it "makes him paranoid about everything".
Paramedics were called to the Balmoral Road address shortly before 9am on October 1 last year to a report that Oskar had been found unresponsive.
He was taken to Royal Lancaster Infirmary but was pronounced dead soon after arrival.
A catalogue of non-accidental injuries were identified in the post-mortem examination, with a total of 13 marks to his face and neck.
There was also bruising to both testicles, with a jury being told such injuries would have caused "immense pain" when Oskar was alive.
Following sentencing, Detective Chief Inspector Jon Holmes, of Lancashire Constabulary's force major investigation team, said: "We welcome the sentence imposed by the court today.
"Kane Kennedy has repeatedly changed his account of what happened on that fateful night and has tried to blame other family members to try to save himself.
"The person who should never be forgotten in this is baby Oskar. He should have been able to look to Kane Kennedy for the protection and love of a parent. Instead this defenceless child found himself subjected to horrendous abuse and the injuries which sadly caused his death.
"My thoughts remain with the wider family of baby Oskar who have been through so much over the last year. I hope that this sentence can offer them some comfort as they try to move on with their lives."