He was spotted "hacking at her" with a knife as he kneeled over her during the attack at their home, the court was told.
Steven Parker, 24, of Dragonby Road, Scunthorpe, denies murdering Jane Parker, 25, on October 27 last year, but admits manslaughter on the grounds of 'loss of control'.
Simon Waley, prosecuting, told Hull Crown Court that Parker had a "weird and glazed over" look on his face shortly before the murder.
Mrs Parker's brother-in-law, Christopher Wood, was waiting for her outside the couple's home when he heard her screaming.
"Once the screaming started, it was continuous," said Mr Waley.
Mr Wood tried to barge his way in and kick the door down but could not do so.
He looked through the dining room window and saw Mrs Parker already slumped on the floor. There was blood on the floor.
"The defendant was kneeling over her and hacking at her with a knife," said Mr Waley.
Mr Wood dialled 999. He managed to break in through the front door.
"When he got in, the defendant was still stabbing at her with a knife," claimed Mr Waley.
Mr Wood grabbed hold of Parker. Mrs Parker was saying: "I'm dead".
There was a struggle between the two men and Mr Wood managed to disarm Parker and restrain him. The struggle continued. Mr Wood released Parker and turned his efforts to Mrs Parker, who was bleeding heavily.
Parker was saying: "What have I done?"
Mr Wood dialled 999 again and was given advice on how to try to resuscitate her.
A paramedic and a police officer arrived.
Parker asked: "Will she be okay?"
Mrs Parker was still alive but efforts at hospital to save her failed and she was later pronounced dead.
Two knives were found at the scene and both had bloodstains on them.
A pathologist later discovered that Mrs Parker's jugular vein and her lung had been cut, causing massive bleeding.
A note written by Parker, begging his wife not to leave him, was found on the living room floor.
After his arrest, scratch marks were found on Parker's body including one on his torso which read "I (heart shape) JP".
He later made 'no comment' in interviews.
The trial, listed for about six days, is being heard before judge Michael Mettyear.
He warned the jury of six men and six women not to 'tweet' or 'Twitter' or to discuss the matter on Facebook.
Parker is being represented by William Harbage QC and Ian Haywood.
Victim had enough of 'possessive' husband
MURDER suspect Steven Parker had become "possessive" towards his wife and she "had had enough" of it, a court heard.
Simon Waley, prosecuting at Hull Crown Court, said that the couple met at school in about 1998.
When she was 16, she became pregnant with their first child, Jessica, born in December 2002.
They moved to Dragonby Road, Scunthorpe, in 2003 and their second daughter, Kaitlyn, was born in 2005. Their relationship began to deteriorate and Jane told her sister, Leann Wood, that Parker had had an affair.
Despite this, they married in October 2006 and a third child, Liam, was born in April 2007.
"He started to become very controlling and possessive in relation to Jane and, even while that was the case, he was ignoring her or neglecting her emotionally," said Mr Waley.
Mrs Parker became more confident after enrolling on a college course and passing her driving test but Parker disliked this.
Her mother, Caron Urch, also saw problems between them, particularly about six months earlier during a caravan break when she overheard Mrs Parker say she would not sleep near him and "a makeshift barricade" had been put between them.
"They had been arguing more recently and all he wanted to do was play on his X-Box and never wanted anything to do with the children," said Mr Waley.
Mrs Parker had been seeing another man, David Lowe, and she told him that Parker paid her no attention, was possessive and would regularly check her mobile phone.
She had told her husband she wanted him out of the house but he said he was not going to leave.
Mrs Parker told her husband's brother, Dean Parker, that he had become "paranoid" about her leaving.
She had, on the day of her death, decided to leave Parker because she "had had enough". She later sent him a text message reading: "I'm sorry, Steve, I will always love you. You have hurt me too much now. I have never forgiven you for Claire so I think it's time for us to separate."
She told him to pack his things and added: "Nothing you say or do will change my mind."
Mrs Urch told the court in a statement that the couple had been suffering problems but married in the hope that it would make them stronger.
They married at Scunthorpe Register office on October 17, 2006 but "things became worse" in their relationship.
Parker had affairs, including with a woman called Kelly, who worked in a factory canteen, and another called Claire who was a friend of Jane Parker.
Jane was 'absolutely devastated' when her friendship with Claire ended because of the affair.
Mrs Urch said her daughter started studying at college and doing Indian head massage, body massage and reflexology and began getting a few clients of her own.
She did so because she wanted to give her three children a good start in life but Parker did not like it and thought the college work was "all going to her head".
Jane had told her mother the couple were "just not getting on and she wasn't happy".
Mrs Urch said: "I told her she must sort it out and make a decision if she was not happy."
Dean Parker, 23, told the court he was aware of the couple's argument and 'bickering' and claimed she told him Parker had "grabbed her by the throat and pinned her up".
He claimed that, on another occasion, Parker hit her on the back of the head, causing her to split her lip on her cup.
Defence barrister William Harbage QC said Claire had denied that "anything sexual" happened between her and Parker. Jane Parker found out about the relationship involving Claire and had an affair of her own to "get back at him", claimed Mr Harbage.
Jane had qualified as a beauty therapist after studying at North Lindsey College, Scunthorpe. At the time of the murder, Parker had been working at the paint factory, Humberside Paint, said Mr Harbage.
The trial continues.