The man accused of killing Sally Anne Bowman flew into a rage when friends suggested he volunteer his DNA to police, the Old Bailey heard this morning.
Chef Mark Dixie, 37, shouted 'Are you f***ing calling me a murderer?', it is claimed.
Victoria Chandler returned to court this morning to continue giving evidence in the trial.
The jury heard yesterday that Dixie had been staying at her house in Avondale Road, South Croydon, after they returned from a camping trip.
On the night of Sally Anne's death Miss Chandler said she had celebrated Dixie's 35th birthday with other friends at the Windsor Castle pub - now the Toby Carvery in Brighton Road, South Croydon.
Asked how he appeared that night, Miss Chandler said: "There was a point his mood changed. He took a phone call and he was quite withdrawn after that."
Miss Chandler said she thought the call was from Dixie's girlfriend Stacey Nivet.
"I believe it was from Stacey. He was expecting her to say happy birthday and instead she asked him to baby sit," she added.
They returned to her flat in Avondale Road, South Croydon, to continue the drinking before going to bed at around 2.30am on September 25, 2005.
Miss Chandler woke up around 10.30am that morning and went downstairs to find Dixie lying on the sofa in the same trousers, the court heard.
Prosecutor Brian Altman asked: "How was the defendant that morning?" and she replied that Dixie was "in good spirits".
Miss Chandler said they went for breakfast but ended up having another pint of lager at the Purley Arms to get over their hangovers.
Two weeks later in October 2005 she was discussing the Sally Anne murder with Dixie and a friend, Justin Everard, and mentioned that the police wanted men in the area to give DNA samples.
Miss Chandler said it was suggested by Mr Everard that Dixie should give a sample.
She said: "He got quite angry. He said, 'Why should I? I was in the flat all night. Are you calling me a f***ing murderer?"
Dixie has since admitted he left the flat during the night and discovered Sally Anne dead 400 yards away in Blenheim Crescent.
He claims he then had sex with her corpse - but denies killing the 18-year-old model.
The trial continues on Monday.
- Click here for full trial coverage
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