Forensic scientist Dr Nigheam Stevenson was giving evidence for a second day at the trial of Colin Coats, 42, David Parker, 38, Paul Smith, 47, and Philip Wade, 42.
All four deny abducting, torturing and murdering Miss Spence at a flat in West Kilbride between April 14 and 28, 2011.
Ms Stevenson told defence QC Derek Ogg, representing Coats, that the investigation at the flat in Meadowfoot Road had been carried out for seven days.
Mr Ogg said: "There have been tremendous forensic resources put into the flat – much more than ordinary scenes."
She replied: "Certainly it was a lengthy investigation."
The defence QC then said: "When the ladies and gentlemen of the jury hear that all that was found was a small blood stain which matched Lynda Spence's DNA and was visible when the police entered the building in October 2011."
Ms Stevenson said: "That was the only DNA matching Lynda Spence."
Mr Ogg then asked if it was possible to find DNA which was invisible to the naked eye and was told it was.
He was told by Ms Stevenson that an additional "very sensitive test" for blood using Luminol was carried out with negative results.
Mr Ogg said: "On CSI and similar programmes an area is sprayed with Luminol and then the lights are switched off. If there is blood present it can be seen for about 30 seconds."
Ms Stevenson confirmed that it is a predictive test for blood, not a positive test.
The QC went on: "If there had been blood there the Luminol would show it up?"
She said this was the case.
The jury was told that the attic area where Miss Spence, who went missing in April 2011, is believed to have been held and tortured, had been tested in this way and no blood had been found.
The floor joists in the attic were also examined and no DNA was found.
The trial before judge Lord Pentland continues.