BLOOD found in a building where a man accused of murdering 18-year-old Kim Newson lived alongside the former Colne teenager was almost certainly hers, a court heard.
A forensic scientist tested bloodstains on stair carpets between the Lincoln flats belonging to Miss Newson and Stephen Charles Hughes.
Peter Hau told Lincoln Crown Court there was a one in a billion chance the blood was that of someone else with the same DNA profile as Miss Newson.
The prosecution alleged the carpets were stained after Hughes attacked the five months pregnant teenager in her flat.
They claim he dragged her down the stairs before dismembering her body and disposing of the remains in the River Witham.
Mr Hau, who works for the Forensic Science Service in Huntingdon, Cambridgeshire, said he compiled a DNA profile of Miss Newson by analysing mouth swabs of her parents, Barry and Wendy Newson. Mrs Newson lives in Burnley.
Prosecuting counsel Nicholas Browne said Hughes told police the stains were the result of a nosebleed the teenager had suffered because of her drug use.
Hughes suggested Miss Newson regularly snorted amphetamine powder but pharmacology professor Paul Nicholls told the court Miss Newson's medical records did not suggest that.
He said those who snorted the drug often suffered nosebleeds because blood vessels in the nostrils were inflamed by the powder. It could also cause a user's blood pressure to rise, he said.
But Mr Nicholls said there was no sign of high blood pressure when Miss Newson was examined by an obstetrician three months before her disappearance.
He agreed mild asthma would make her more susceptible to nosebleeds.
Earlier in the trial the teenager's boyfriend was one of a number of witnesses who said she only swallowed the drug and never snorted it.
Hughes, 41, denies murdering Miss Newson between March 4 and March 29 last year.
(Proceeding)
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