ALEX CHADWICK, host: If Mark Emery ever is convicted in the US, he may someday be required to      wear an electronic monitoring bracelet of the kind famously worn by      Martha Stewart earlier this year.  One was also worn by the Puerto Rican      nationalist leader Filiberto Ojeda Rios before he snipped it off 15 years      ago and went on the lam until last Friday, when he died in a shootout      with FBI agents.  That got the Explainer team at the online magazine      Slate wondering just how easy is it to cut off one of those things.  Here      with the answer is Slate's Andy Bowers.</s>ANDY BOWERS reporting: All you need is a pair of scissors.  Electronic monitoring bracelets      aren't designed to stay on at all costs.  A device that needed special      tools to be removed would pose a serious health risk to its wearer.  A      bracelet might get caught in heavy machinery, for example, or paramedics      might need to remove it to provide emergency medical care.  Most of the      monitoring bracelets on the market can be easily cut in two or even      ripped off if enough pressure is applied.  Of course if you slice through      your bracelet, you'll probably set off an alarm.  A radio transmitter      embedded in the bracelet is programmed to send a distress signal as soon      as it's tampered with, although bracelet manufacturers won't discuss the      specifics.</s>ANDY BOWERS reporting: When a criminal has served his time, removing the bracelet is as simple      as cutting it off.  The actor Robert Blake wasted no time in removing his      monitoring bracelet after being acquitted of murdering his wife.  He      asked the crowd outside the courthouse for a cutting implement moments      after the verdict.</s>ALEX CHADWICK, host: Andy Bowers is a Slate senior editor, and that Explainer was      compiled by Daniel Engber.</s>ALEX CHADWICK, host: NPR's DAY TO DAY continues.  I'm Alex Chadwick.
More and more corrections officials are using electronic bracelets to keep track of prisoners. Slate senior editor Andy Bowers explains why these devices are so easy to remove, and how prisoners can "disappear" from under the watchful eyes of prison guards.