Help making Captcha non case sensitive

Currently the captcha required to submit feedback is case sensitive. Although its not a big deal, I would prefer that it not be. Below is the code inside the contact form file. I thought it would be as easy as removing “require ‘captcha/rand.php’;” from line 8 but that didn’t seem to work. I’m at a lose. Any help is much appreciated.

<?php
/*
Template Name: Contact Form
*/
// Make the page validate
//@ini_set('session.use_trans_sid', '0');

// Include the random string file
require 'captcha/rand.php';

// Begin the session
@session_start();

// Set the session contents
if (isset($_POST['captcha'])){
	if($_POST['captcha']!=$_SESSION['captcha_id']){
		$_SESSION['captcha_id'] = $str;
	}
}
else{
	$_SESSION['captcha_id'] = $str;
}

//If the form is submitted
if(isset($_POST['submitted'])) {
	//Check to see if the honeypot captcha field was filled in
	if(trim($_POST['checking']) !== '') {
		$captchaError = true;
	} else {
		//Check to make sure that the name field is not empty
		if(trim($_POST['contactName']) === '') {
			$nameError = __('You forgot to enter your name.', 'tstranslate');
			$hasError = true;
		} else {
			$name = trim($_POST['contactName']);
		}
		//Check to make sure that the =subject field is not empty
		if(trim($_POST['subject']) == '') {
			$subjectError = __('You forgot to enter the subject.', 'tstranslate');
			$hasError = true;
		} else {
			$nameSub = trim($_POST['subject']);
		}
		//Check to make sure sure that a valid email address is submitted
		if(trim($_POST['email']) === ''){
			$emailError = __('You forgot to enter your email address.', 'tstranslate');
			$hasError = true;
		} else if (!eregi("^[A-Z0-9._%-]+@[A-Z0-9._%-]+\.[A-Z]{2,4}$", trim($_POST['email']))){
			$emailError = __('You entered an invalid email address.', 'tstranslate');
			$hasError = true;
		} else {
			$email = trim($_POST['email']);
		}
		//Check to make sure sure that a valid captcha is submitted
		if(trim($_POST['captcha']) === ''){
			$captchaError = __('You didn´t type the captcha.', 'tstranslate');
			$hasError = true;
		} else if ($_SESSION['captcha_id'] != $_POST['captcha']){
			$captchaError = __('You entered an invalid captcha.', 'tstranslate');
			$hasError = true;
		} else {
			$_SESSION['captcha_id'] = $str;
		}
		//Check to make sure comments were entered
		if(trim($_POST['comments']) === ''){
			$commentError = __('You forgot to enter your comments.', 'tstranslate');
			$hasError = true;
		} else {
			if(function_exists('stripslashes')){
				$comments = stripslashes(trim($_POST['comments']));
			} else {
				$comments = trim($_POST['comments']);
			}
		}
		//If there is no error, send the email
		if(!isset($hasError)){
			$emailTo = get_option('themeshock_contact_mail');
			$name = trim($_POST['contactName']);
			$subject = trim($_POST['subject']);
			$sendCopy = trim($_POST['sendCopy']);
			$body = "Name: $name \n\nEmail: $email \n\nMessage: $comments";
			$headers = "From: $name <$email>" . "\r\n" . 'Reply-To: ' . $email;
			wp_mail($emailTo, $subject, $body, $headers);
			$emailSent = true;
		}
	}
} 

get_header();
wts_tool_panel('end-layout-3');	wts_tool_panel('layout-4');
?>
<div class="wrapper_content">
  <div class="lay_base content_pattern"></div>
  <div class="bar_separate footer_separate"></div>
  <div class="lay_base content_shadow"></div>
	<div id="content">
		<div class="contact_form boxcss_3">
			<h1 class="text-center"><?php the_title(); ?></h1>
				<?php if ( $_SERVER['HTTP_HOST']==='www.wpthemegenerator.com'):?>
        <style>
					p.info_tg{
						padding:0 17px;
					}
				</style>
					<p class="info_tg">	This is a sample contact form that shows how the contact form will look in our themes, if you have questions please use this <a href="http://www.wpthemegenerator.com/contact/">contact form</a></p>
				<?php
				endif;
			 if(isset($emailSent) && $emailSent == true) {?>
      <div class="thanks">
        <h1><?php echo __('Thanks','tstranslate'); $name;?></h1>
        <p><?php echo __('Your email was successfully sent. I will be in touch soon.','tstranslate');?></p>
      </div>
      <?php } else {
				if (have_posts()) : while (have_posts()) : the_post();
					if(isset($hasError) || isset($captchaError)) { ?>
      		<p class="error"><?php echo __('There was an error submitting the form.','tstranslate');?><p>
          <?php } ?>
      <form method="post" action="<?php the_permalink();?>" id="contactForm" class="contactForm">
        <table id="contact_us" align="center">
          <tr>
            <th><?php echo __('Name','tstranslate');?></th>
            <td>
              <input name="contactName" type="text" class="requiredField" id="contactName" value="<?php if(isset($_POST['contactName'])) echo $_POST['contactName'];?>" size="30"/>
              <?php if($nameError != '') {?>
                <span class="error"><?php echo $nameError;?></span>
              <?php } ?>
            </td>
          </tr>
          <tr>
            <th>E-mail</th>
              <td>
                <input type="text" name="email" id="email" value="<?php if(isset($_POST['email']))  echo $_POST['email'];?>" class="requiredField email" size="30"/>
                <?php if($emailError != ''){?>
                  <span class="error"><?php echo $emailError;?></span>
                <?php }?>
              </td>
          </tr>
          <tr>
            <th><?php echo __('Subject','tstranslate');?></th>
            <td>
              <input type="text" name="subject" id="subject" value="<?php if(isset($_POST['subject']))  echo $_POST['subject'];?>" class="requiredField subject" size="30" />
              <?php if($subjectError != ''){?>
                <span class="error"><?php echo $subjectError;?></span>
              <?php }?>
            </td>
          </tr>
          <tr>
            <th><?php echo __('Message','tstranslate');?></th>
            <td>
                <textarea name="comments" id="commentsText" rows="10" cols="80" class="requiredField"><?php if(isset($_POST['comments'])) { if(function_exists('stripslashes')) { echo stripslashes($_POST['comments']); } else { echo $_POST['comments']; } } ?></textarea>
              <?php if($commentError != '') {?>
                <span class="error"><?php echo $commentError;?></span>
              <?php }?>
            </td>
          </tr>
          <tr>

<th>Captcha</th>
            <td>
              <label for="captcha"><?php __('Enter the characters as seen on the image below:','tstranslate');?></label>
              <div id="captchaimage">
                <img src="<?php echo get_template_directory_uri(); ?>/captcha/images/image.php?<?php echo time(); ?>" width="132" height="46" alt="Captcha image" />
              </div>
              <input type="text" maxlength="6" name="captcha" id="captcha" />
              <?php if($captchaError != '') {?>
                <span class="error"><?php echo $captchaError;?></span>
              <?php }?>
            </td>
          </tr>
          <tr class="field_span">
            <td></td>
            <td>
              <label for="checking" class="screen"><?php echo __('If you want to submit this form, do not enter anything in this field','tstranslate');?></label>
              <div class="clear"></div>
              <input type="text" name="checking" id="checking" class="screenReader" value="<?php if(isset($_POST['checking']))  echo $_POST['checking'];?>" />
            </td>
          </tr>
          <tr class="btns-send">
            <th></th>

            <td>
                <input type="hidden" name="submitted" id="submitted" value="true" />
                <input type="submit" name="submit" id="submit" class="sended" value="<?php echo __('Send','tstranslate');?>"/>
            </td>
          </tr>
        </table>
      </form>
      <?php endwhile;  endif; }?>
    </div><!-- end contact form -->
	</div><!-- content -->
</div><!-- end wrapper content -->
<?php get_footer();?>