A forensic expert in the Angelika Kluk murder trial has conceded she did not swab all of a piece of tape used to gag the Polish student.
Carol Weston told the jury about blood-stains she found
Carol Weston said a print provided DNA which closely matched the accused Peter Tobin but said in hindsight she should have swabbed the whole tape.
The High Court in Edinburgh also heard there was no DNA linking her death to a priest who admitted sleeping with her.
Peter Tobin, 60, denies raping and murdering Angelika and other charges.
Father Gerry Nugent, 63, gave a DNA sample to detectives investigating the Polish student's murder.
But forensic scientist Mrs Weston, 33, said the test had shown nothing to link the priest to Angelika's death.
Appearing as a witness for the second day, Mrs Weston told the court that Father Nugent, and a number of other people, had been asked to give DNA samples "for elimination purposes".
They included Angelika's married lover Martin Macaskill and his wife Anne. Mrs Weston said there was no evidence to link any of them, in terms of DNA profiles, to Angelika's dead body.
The forensic scientist had earlier described how a fleece jacket and a tarpaulin sheet with Angelika's blood on them had been found.
Mrs Weston said the blood smears would be consistent with a body being wrapped in a sheet and then slid under the church floor.
Mrs Weston had been called in when Angelika's blood-stained body was found bound and gagged under the floor of St Patrick's Church in Anderston, Glasgow, where Father Nugent was the parish priest.
She had previously told the High Court in Edinburgh of DNA tests linking Mr Tobin and Angelika.
Defence counsel Donald Findlay QC asked if she had taken a swab from the tape background in the area of the ridges supposedly left by Mr Tobin's finger.
"No I didn't. I am not sure why I didn't," said Mrs Weston.
The lawyer said: "So the DNA may have been on the tape and you have not been successful in profiling the ridges?"
Mrs Weston replied: "It is a possibility, yes."
Mr Tobin denies murder, attempting to defeat the ends of justice, attempting to pervert the course of justice and breach of the peace.
He also denies rape, claiming he had sex with Angelika with her consent.
Angelika, 23, had been staying at the chapel house attached to St Patrick's Church in Anderston, Glasgow, and working as a cleaner to help finance her language studies in Gdansk.
Mr Tobin was helping out there as an odd job man.
He is accused of attacking Angelika between September 24 and September 29 in St Patrick's Church, or elsewhere, gagging her with cloth and tape, binding her hands with cable ties, raping her, smashing her skull with a piece of wood or something similar, stabbing her 16 times in the chest and inflicting other knife injuries.
It is alleged that he then hid the body under the floor of the church.
A further charge alleges that he told Glasgow police his name was Patrick McLaughlin, gave a false date of birth and address, and that he travelled to London and gave staff at the National Neurology and Neurosurgery Hospital in Queen's Square, London, another false name.
Mr Tobin also denies a breach of the peace between July and September last year by threatening Russian student Rebecca Dordi at St Patrick's Church.
The trial continues.