If you're headed out for some New Year's Eve festivities, first a word from area police.  Despite the popularity of those portable breath tests, state troopers say leave them at home.

The portable breathalizers are marketed as a way to keep you safe while celebrating, but police say they provide a false sense of security that could land you behind bars... or worse. 

Each new year's brings the threat of a celebration turning into a tragedy.  Police try to prevent it by strictly enforcing DWI laws. 
But more and more partiers are taking the law into their own hands with the help of these personal breath alcohol tests.  Sold for about $10 each, they claim to detect blood alcohol levels above .02 with 99% accuracy.  "The positive side is a least people are aware that there's a problem," said Lt. Terry Moore with the MO Highway Patrol Troop D.
 

But he says the negatives far outweigh positives.  First, he's concerned about the accuracy of the device.  "If you're buying $10 instrument that's supposed to do same as $3 or 400 instrument then you get $10 results."
 
But far more worrisome, Lt. Moore says, is that people who buy these are most likely intending to drink and drive.  "People using these are going to events where they know they're gonna have a lot of drinks and they're concerned about achieving certain level rather than being impaired."
 
Not to mention that you're asking someone who could potentially be impaired to properly use the instrument and have the good judgement to not get behind the wheel should the test be positive.  Lt. Moore says there's a much better way to prevent this.  "It's not okay to be impaired and drive and only way to assure this is to not drink."

One thing to keep in mind, police say, is that when you leave a bar, your alcohol level may not have peaked. It keeps rising as the alcohol moves from your stomach into your bloodstream.