It turns out that all cellphones, even those without apps, can serve as a very particular type of lie detector. And the detector tells us many people are not just liars, but filthy liars.

The London School of Hygiene and Tropical Medicine has been working with Queen Mary, University of London to carry out a study designed to promote Global Handwashing Day, which takes place tomorrow. The study involved interviewing 390 people across 12 cities, then taking samples from both their hands and their cellphone.

Of those surveyed, 95 percent claimed that they always wash their hands after using the toilet, with soap wherever possible. That was somewhat undermined by the discovery that 82 percent of people had bacteria on their hands (of a type that should have been killed by washing with soap) while 92 percent had bacteria on their phones.

It also emerged that 16 percent of people and 16 percent of phones had traces of E.coli. Bearing in mind phones rarely suffer from food poisoning, the clue to the origin of that contamination is the researchers’ description of E.coli as “bacteria of a faecal origin”, which brings a whole new meaning to having a crappy phone.

The Daily Telegraph notes that cellphones make a perfect home for bacteria: the surfaces are regularly heated up when the device is used, it’s difficult to properly clean the surface (and most of us rarely try), and we even supply the bacteria with a source of protein when we make a call and ignore the schoolyard plea to “say it, don’t spray it.”

And of course, once bacteria is on a phone, it’s ready to get back on to our hands when we use it, or even get into scratches on the ears and face when we make a call.