Blood stains on the clothes of a man accused of murdering his teenage sister could be “attributed to an assault”, a forensic biologist has said.

DNA samples taken from the clothing of Connor Gibson, 20, found “widespread blood staining” on the accused’s jacket which experts said was compatible with 16-year-old Amber Gibson.

He is accused of assaulting and sexually assaulting his teenage sister, removing her clothes and repeatedly inflicting blunt force trauma to her head and body in November 2021.

Her body was discovered on November 28 2021 at Cadzow Glen in Hamilton, South Lanarkshire.

Amber Gibson death
The scene at Cadzow Glen park in Hamilton where the body of Amber Gibson was discovered (Lucinda Cameron/PA)

Alana Gunn, forensic biologist, told the trial at the High Court in Glasgow on Tuesday the blood found on the jacket, which was hanging in his room at the Blue Triangle hostel in Hamilton, also “appeared mixed with mud and dirt staining”.

Jurors heard how the DNA profile compatible with Ms Gibson was estimated to be “about one billion times more likely” to be from her than an unrelated individual.

Advocate depute Richard Goddard asked Ms Gunn: “There was widespread blood staining found on the front and both sleeves of the jacket?”

She said: “Yes, it was on a large area of the jacket.

“The DNA profile in other areas of the jacket which were examined could be explained by Amber Gibson as a major contributor and Connor Gibson as a minor contributor.”

The advocate depute asked: “That could be explained by Connor Gibson being involved in an assault of Amber Gibson?”

Ms Gunn replied: “Yes, it could be attributed that way. It is an overall interpretation given the blood staining as contact blood staining.”

Further blood stains were found on Gibson’s white and grey Adidas Gazelle trainers, which were found on the floor of his room.

The stains included a dropped spot of blood matching Amber Gibson’s DNA which could have come from an “open wound”, Ms Gunn said.

His DNA was also found on jogging bottoms and shorts, worn as underwear, which had been removed from the victim’s body.

Gibson is also alleged to have compressed the 16-year-old’s neck with his hands and strangled her with the intention to rape her.

He is further accused of attempting to defeat the ends of justice by disposing of bloodstained clothes, and calling the children’s home where his sister was living and pretending she was alive.

He also faces a charge of attempting to pervert the course of justice by telling police he had argued with his sister on the evening of November 26 before going to someone’s home.

Gibson’s defence agent, Tony Graham, asked Ms Gunn if it was possible the DNA evidence linked to the accused on his sister’s clothes could have been “secondary transfer” from being in close proximity while taking a photograph. Ms Gunn agreed it was possible.

Mr Graham then asked if the DNA evidence linked to Gibson on his sister’s clothes could have been “secondary transfer” as a result of this contact when taking a photo of the pair, to which Ms Gunn said it was possible.

Mr Graham also asked if it was true that DNA evidence from Gibson had not been found on Ms Gibson’s breasts, buttocks or intimate areas. She agreed it had not.

The court earlier heard that Ms Gibson had died from strangulation.

Mr Graham put it to Ms Gunn, while there was evidence to suggest Ms Gibson was struck on the nose, “you could not provide evidence which suggested he (Gibson) murdered Amber Gibson?

“She didn’t die of a blow to the nose. On that basis, would you accept that no part of the DNA jigsaw you bring to the court points to Connor Gibson?”

Ms Gibson said she could not comment on the claims but said there was no evidence to suggest “who came into contact with her neck” based on the findings.

A second man, Stephen Corrigan, 45, is also on trial.

He is accused of discovering Amber’s body between November 26 and 28 last year but instead of alerting police, he is alleged to have inappropriately touched her and concealed her body.

Both men deny all charges against them, with Corrigan’s defence agent Rhonda Anderson submitting a special defence of alibi on his behalf.

Jurors heard that Corrigan’s DNA on the victim was “widespread” and included 39 areas of her body, including her buttocks, breasts and pubic area.

Ms Gunn told the court: “In our opinion, based on the collective findings relating to Stephen Corrigan, it could be explained if he had direct contact with Amber Gibson while she was unclothed.

She also said the evidence did not suggest that Ms Gibson had redressed after Corrigan’s DNA had been on her body, and added that the presence of his DNA could “not be explained by the statement that he had never had any contact with Amber Gibson”.

The trial, before Lord Mulholland, continues.