A man accused of throwing his girlfriend over the balcony railing of a fourth-floor flat has told a court he "stumbled into her".
John McAleer, 24, of Belsize Road, Hemel Hempstead, had pleaded not guilty to the attempted murder of Danielle Hammond, 21.
He told St Albans Crown Court he was pushed by someone else in the flat and fell onto Ms Hammond.
She fell 45ft (13.7m) to the ground below and suffered severe injuries.
The court heard the couple had been drinking with friends in Hemel Hempstead on the evening of 29 June before going to Mr McAleer's sister's flat in Lord Alexander House.
The prosecution claims the defendant deliberately pushed Ms Hammond over the balcony railing during a row in the early hours of 30 June.
She suffered a fractured skull, bleeding around the brain, major trauma to her internal abdominal organs, a loss of hearing and speech impairment.
She has no memory of the events and will not be giving evidence due to her injuries.
The prosecution said earlier that evening Ms Hammond had ended up on the floor in the flat and told a female friend Mr McAleer had pushed her.
Prosecutor Ann Evans said one of the others, Jake Hulse, saw the pair on the balcony where Ms Hammond was sitting on the railing and appeared to raise her right leg up.
Mr McAleer walked towards her, "grabbed her leg, pushed it up and threw her over the balcony" and then told Mr Hulse she had fallen, she said.
In the witness box, Mr McAleer said Mr Hulse had pushed him from behind and so he "stumbled forward and put my arms out".
"I went forward and knocked her off balance," he said.
"She fell backwards and I tried to grab her leg as quickly and as tightly as I could, but she was sliding through my hands as she was falling back."
He told the court it felt "like my whole world had come crashing down... She was the love of my life".
The trial continues.