A TEENAGER accused of murdering his six-week-old son told a jury how he took illegal drugs at a party just hours before the baby's death.

The 17-year-old, who cannot be named for legal reasons, admitted drinking and taking MDMA at a gathering at a neighbour's flat – hours before the baby suffered fatal injuries.

But the teenager, who is accused of murder for causing the infant to suffer injuries including a skull fracture, broken leg and rib fractures, also told a jury the birth of his son was "the best day of my life".

He added: "He was the best thing that happened to me and always will be."

Appearing at Winchester Crown Court on the opening of the defence's case, the defendant, who was 16 at the time, said that he and the mother had gone to a gathering at a neighbouring flat.

He said he drank Corona and Budweiser lager before also drinking vodka and taking MDMA.

The defendant, who told the court he suffers from memory problems, said he did not recall returning to his partner's flat, where he then remembers seeing her crying with the baby in her arms.

He said: "(She) was sat on the bed with (the baby) in her arms in a very bad state. She was crying, panicking, shaking.

"I walked in and she stood up and said he was white, he wasn't breathing, she didn't know what to do, I said 'call an ambulance'.

"She got up and said he wasn't breathing, he was grey and white, she passed him to me, he wasn't moving, he was literally stone cold, I was hugging and squeezing him, I didn't know what to do until the ambulance was on the phone and told me what to do."

He said that he performed CPR on the baby as instructed over the phone until the paramedics arrived to take the child to hospital, where he later died.

The defendant said he did not remember saying to a neighbour: "What have I done?"

He added that the mother, who is now aged 19, had told him the baby had fallen off the sofa on to the hard floor.

He denied having "intentionally" caused the child any harm and said he had never stopped loving him.

The seven-week-old baby was bitten on the nose in the alleged attack which happened at the mother's Southampton flat in the early hours of February 11.

The baby's mother, aged 18 at the time, is on trial for child cruelty for failing to protect her baby or seek help for him.

The defendant said that he had been told that he had been "heavy-handed" with the baby when he had first looked after him but said he had taken in the criticism and "realised what I was doing wasn't appropriate".

Describing the birth of his son, the defendant said: "I was in a bit of a state, I was happy, it was the best day of my life."

He added: "He was the best thing that happened to me and always will be."

He said that he did not remember pushing the child's mother to the ground in October 2017 while she was still pregnant, causing a bruise to her face, and said he was "devastated" that he had hurt her.

The defendants deny the charges and the trial continues.