More recently, DNA 'dragnetting' has seen Police ask to volunteer blood or saliva samples to aid in investigations where genetic evidence has been collected from a crime scene but no known suspect has been identified.

Police say they won't act on Google location details alone when making an arrest, but the practice has already seen innocent people detained for crimes they didn't commit (stock image)

The law would allow European prosecutors to force companies to turn over data such as emails, text messages and pictures stored online in another country, within 10 days or as little as six hours in urgent cases.

The European Union executive says the proposed law, which would apply to data stored inside and outside the bloc, is necessary because current legal procedures between countries to obtain such electronic evidence can drag on for months.

Stacey White accused the social media giant of denying her justice after police were forced to apply to American judges for a court order demanding that it hand over the information.

Detectives investigating 13-year-old Lucy's murder were desperate to access Facebook accounts belonging to tattoo artist Stephen Nicholson, who was jailed for 14 months for refusing to reveal his password to police.