New surveillance-CSI method: Beverage hair-isotope trail
Gloves? Check. False numberplates? Check. Perrier...?
International master criminals, spies, investigative journos, subversives, rebels and others who may find government agencies trying to monitor your movements: take note.
You already, of course, make sure never to travel in a vehicle whose numberplate can be linked to you, for fear of generating a trace in the ANPR traffic-cam databases. You always purchase travel tickets or Oyster cards  or taxi rides for cash, to avoid leaving a glistening trail of card transactions for spooks or cops to follow. You never turn on a cellphone, Wi-Fi or Bluetooth enabled device without considering that its unique identification signatures could give your identity (or your previous presence at some other time or place of interest) away to interested parties.
You never, ever leave fingerprints or DNA in compromising places: you probably wear gloves a lot, and may even go so far as to blow up any vehicles of interest to the authorities once you've finished with them using a simple blast-incendiary device.
You do all this, but you probably don't take enough care about what you drink. That's a mistake.
It's a mistake because one day the minions of the state, having lost track of you for several days during which you went somewhere and did something you would rather not discuss with them, will pull you in anyway even though they've got nothing. They'll ask you, perhaps, whether you've been to city X where event Y has just taken place.
Confident that you left no cells or fingerprints or incovenient database entries behind you, you'll deny any such trip with a cocky smile.
Then they take a sample of your hair and analyse it. Perhaps if you're a real big fish and you're dealing with counterterror or counterespionage operatives, they don't even pull you in for this: they simply break into your home covertly and snitch some samples off your hairbrush.
Either way, you're now well on the way to being stuffed. The hair samples reveal the varying proportions of different isotopes of hydrogen and of oxygen in the water you have lately been ingesting as part of your drinks.
And it turns out that this can be used to identify just where that water came from. It's long been known that this can be done with tap water, but it now turns out that even in the cases of bottled water, pop and beer the distributive trades generally source their water pretty close to the point of consumer sale.
Boffins at the University of Utah, having analysed beer, pop, bottled and tap water from 33 US cities, reckon that hair samples can give valuable info about just where the owner of the hair has lately been quaffing beverages.
According to this statement  from the American Chemical Society, discussing the Utah research:
The finding may help trace the origin of drinks or help criminal investigators identify the geographic travels of crime suspects and other individuals through analysis of hair strands.
So in future when planning that trip, mission, meeting or operation that absolutely had better not be reconstructed by the authorities later, you'd probably do well to take some water with you - or lay in something from far afield, perhaps, just to confuse the CSI types later.
One should note that the Utah researchers in question are hoping to sell this idea for money , so it's quite possible they're exaggerating the "iso-signature" technique's effectiveness and accuracy. It's still one to take note of, though.
A full scholarly paper describing the underlying results can be read for free here . ®