Offenders were far harder to trace than ever before, he added, since they were now communicating through the internet and social media, rather than by phone, and sometimes leaving "no footprint".

BBC: Computer keyboard and mouse

While police have so far found no trace of Ms Rushworth, who disappeared in June 2009, body parts belonging to the other two women have been found in the River Aire in Bradford.

BBC: Vigil for Bradford deaths women

These devices mimic the human nose and human tongue but have far greater sensitivity to trace scents and flavors.

FORBES: Magazine Article

Officers have carried out a number of inquiries in a bid to locate her but so far have found no trace.

BBC: Debbie Starbuck

No arrests have been made so far but police want to trace two men seen running away from Hindrey Road.

BBC: Joseph Burke-Monerville

They have accepted that their liability goes far beyond what accountants will be able to trace in the banks' books.

ECONOMIST: Switzerland off the hook

Ms Werning therefore decided to trace the phenomenon of rapid growth back as far as she could in the fossil record, by examining the bones of a wide variety of species.

ECONOMIST: Or, rather, the dinosaur and the crocodile