Radio group default being stripped out?

<ul class="radio">
<li><input type="radio" name="reason" value="1" title="Enquiry about further information" class="radio" id="radio1" checked="checked" /><label for="radio1">Enquiry</label></li>
<li><input type="radio" name="reason" value="2" title="Comment on the web site" class="radio" id="radio2" /><label for="radio2">Comment on the web site</label></li>
<li><input type="radio" name="reason" value="3" title="Report a technical problem or error" class="radio" id="radio3" /><label for="radio3">Report a technical problem or error</label></li>
</ul>

//<?php
   //if no postback, retain any checked values
    if(!$isPostBack && !empty($tagAttributes['checked'])) $fields[$name][]=stripTagQuotes($tagAttributes['value']);