Forensic scientist Andrew Davidson, 46, carried out DNA analysis on various items of clothing found on the bodies of Christine Eadie and Helen Scott.
These included tights and belts used as ligatures to bind the girls.
Mr Davidson, who works for the Chorley-based organisation Cellmark, co-authored a report on the findings with forensic scientist Geraldine Davidson, the jury was told.
The High Court in Livingston has already heard six days of evidence from Ms Davidson about the results contained in the report.
Calling Mr Davidson to give evidence, prosecutor Lord Advocate Frank Mulholland said: “I can indicate that this is the last prosecution witness.”
Angus Sinclair, 69, is on trial at the court for a fourth week, where he denies raping and murdering the girls.
He is accused of carrying out the attacks along with his brother-in-law Gordon Hamilton, who is now dead.
Christine and Helen, both 17, were last seen at the World’s End pub in Edinburgh on October 15 1977.
Christine’s body was found the following afternoon at Gosford Bay in Aberlady, East Lothian, while Helen’s body was discovered a few hours later in a wheat field near Haddington.
Jurors have been told that Sinclair claims the girls were “alive and unharmed” when he left their company.
He has lodged three special defences, of consent, alibi and incrimination.