It can give dupes. In fact sometimes, the letters are so bad that the best the contestants can do is get a 4-letter word.

I couldn't find the offical Countdown website on channel4.com. But there is more info about how the game is played here.

Simon Flack ($code or die)
$,=reverse'"ro_';s,$,\$,;s,$,lc ref sub{},e;$,
=~y'_"' ';eval"die";print $_,lc substr$@,0,3;