Anti-terrorist skills were used in the hunt for the killer of student Zoe Nelson, whose badly burnt body was found dumped among scrub on an old coal bing in Lanarkshire in May last year.
Detective Constable Jennifer Bell, 34, told the High Court in Edinburgh she trawled though hours and hours of film taken that weekend by CCTV cameras in Wishaw.
The court heard that Detective Constable Bell had previously used her skills in the aftermath of the July 7 bombings of London tube trains and a bus in 2005 and after the Glasgow Airport bombing.
She had spent 18 months with the Metropolitan Police after being seconded to their counter-terrorism command.
Along with the jury, Detective Constable Bell watched again footage from security cameras at an Asda store in Newmanins, Wishaw, a ScotMid shop in the town's Manse Road and cameras mounted at Cambusnethan children's home.
She said that while watching the films she had been asked to look out for individuals wearing clothing which was deemed relevant.
The cameras had caught shots of a man believed to be Robert Bayne in the company on Zoe on May 22 last year.
Bayne, 21, of Harper Crescent, Cambusnethan, Wishaw, denies murdering the 17-year-old mechanics student that day then torching her body as part of an attempted cover-up.
He also denies taking Zoe's sister, Laura Anne to show her the body, threatening to kill her if she told what she had seen.
Bayne is accused of attacking mechanics student Zoe with a knife near Branchalfield Drive, Cambusnethan, at a spot known locally as Monkey Hill, putting a plastic sheet over her head to restrict her breathing and then setting fire to her.
Bayne also denies an earlier attack on Zoe of Crindledyke Crescent, Newmains, by punching her on the head and scratching her and, on another occasion, committing a breach of the peace by threatening her.
It is also claimed that after the murder he tried to cover up his alleged crime by setting fire to Zoe's body, washing his clothes, dumping her mobile phone and telling police that someone else was responsible.
Bayne denies all the charges against him, including an alleged assault on a detective and repeatedly stealing booze from an Asda store in Morningside Road, Newmains, on the day Zoe is said to have died. The trial continues.