A man bludgeoned his baby son to death with a hammer after telling his partner it was a “special night”, a court has heard.
Bidhya Sagar Das, 33, killed 16-month-old Gabriel Sonu Bibekas while the child's mother was in the shower at their home in Finsbury Park, north London, on 18 March.
The couple's relationship had been rocked by Das's paranoid suspicions that cleaner Christinela Datcu was having sex with other men while he was at work.
But on the night of the killing, Das gave Ms Datcu a foot massage and told her “it's going to be a special night”, the Old Bailey was told.
As she got out of the shower, Ms Datcu heard crying and rushed into Gabriel's bedroom “to find a scene that was the stuff of nightmares”, prosecutor Zoe Johnson QC said.
Gabriel was covered in blood, having suffered multiple skull fractures. He was pronounced dead later the same night.
A young girl, who cannot be identified for legal reasons, also had “terrible head injuries” but survived, Ms Johnson said.
After killing Gabriel, Das left the flat and dumped a large claw hammer in a nearby skip.
Meanwhile, panic-stricken Ms Datcu rushed to a neighbour to raise the alarm, screaming that her baby had been killed.
Last month, hotel worker Das pleaded guilty to Gabriel's manslaughter by diminished responsibility and the attempted murder of the other child, following psychiatric reports.
The court heard that the couple met at the Central Park Hotel in Finsbury Park where they both worked.
When Ms Datcu fell pregnant, cannabis smoker Das initially told her he did not want children because he was not a strong person.
After Das failed to turn up for work on 14 March, he told his manager that his partner was being unfaithful.
He went to social services and said to the manager he loved Gabriel “too much, too much”.
Ms Johnson said Das's suspicions of infidelity were “completely unfounded” and caused “significant difficulties between the couple”.
Das left his mobile phone in their bedroom to record what she was doing while he was out, Ms Johnson said.
“His paranoia resulted in him repeatedly calling her from work to check up on her, and then to leaving work during his night shifts to come home to see what Ms Datcu was doing and to search for men he believed were hiding in the flat,” the lawyer said.
Das had assaulted his partner at least three times as he accused her of being unfaithful, the court heard.
Ms Johnson said: “Things got so bad that on the occasions when they spent the night together he removed his shoe laces and tied Ms Datcu's underwear to his own, to ensure that she could not get up without him knowing.”
Ms Datcu was “concerned” about his behaviour but stood by him for the sake of their child.
But she was “shocked and upset” to get a call from social services about Das's allegation that she was an “unfit mother”, days before the killing, Ms Johnson said.
Just before the attack, Das had told a friend he was going to “kill Christina because she f**** men”, the court heard.
The day after the killing, Das called police and confessed, saying: “Saturday night I did very bad, honestly.”
Ms Datcu was not in court when Das appeared for the first of a two-day sentencing hearing, and said in a victim impact statement: “I never want to see the face of my child's father again.”
She described Gabriel as her “miracle baby” after she had been told by doctors in Britain and her home country of Romania that she might never conceive.
She said: “The future seemed wonderful, that the father was supporting me. There is no more beautiful thing to me than being a mother.”
Following the attack, she said she felt “like a robot” and it was “just a question of survival”.
She said: “After the incident, I could hardly sleep at all. Recently after 40 days, Gabriel started to appear in my dreams and I started to sleep better.”
The court heard that the injured girl faced “life-long” medical problems as a result of the attack.
Mr Justice Spencer will sentence Das on Friday.