Custom ReCaptcha Login

I’m trying to add ReCaptcha to my login page. I know there are many many plugins by per request I cannot use plugins. So far so good, I’m able to add the Captcha to my login but unable to show errors.

It will error out on me when I enter the wrong password, but if I enter the right password and do not enter the Captcha I get no errors (which I should get a Captcha not filled error). So the only time my captcha_errors function fires is when user name / password is wrong.

How do I get my login form to check the ReCaptcha before checking the login credentials?

do_action('login_head');

// this function adds captcha to the login form
function addCaptcha() {
    if( session_id() == "" )
        @session_start();

    if (isset( $_SESSION["recaptcha_response_field"] )) 
        unset( $_SESSION["recaptcha_response_field"] );

    ?>
        <p class="cptch_block">
            <div id="cap"></div>
            <script type='text/javascript' src='http://www.google.com/recaptcha/api/js/recaptcha_ajax.js'></script>
            <script type='text/javascript'>
                Recaptcha.create("pubk", "cap", {theme:"clean", callback: Recaptcha.focus_response_field});
            </script>
            <noscript>
                <iframe src='http://www.google.com/recaptcha/api/noscript?k=pubk' height='300' width='500'></iframe>
                <br />
                <textarea name='recaptcha_challenge_field' rows='3' cols='40'></textarea>
                <input type='hidden' value='manual_challenge' name='recaptcha_response_field'/>
            </noscript>
        </p>
        <br />
    <?php 
    return true;
}

function verifyCaptcha($pageid) {
    $result = false;
    if( session_id() == "" )
        @session_start();

    $pvk = 'prvk';

    if (!empty($pvk) && isset($_POST['recaptcha_response_field'])) {
        if(!function_exists('recaptcha_check_answer')) {
            require_once 'recaptchalib.php';
        }
        $resp = recaptcha_check_answer($pvk, $_SERVER['REMOTE_ADDR'], $_POST['recaptcha_challenge_field'], $_POST['recaptcha_response_field']);
        $result = $resp->is_valid;
    }
    if(!$result)
        return $_SERVER["REQUEST_URI"];
    else
        return admin_url();
}


// this function checks captcha posted with a login
function captcha_errors( $errors ) {
    if ( isset( $_SESSION['cptch_error'] ) )
        unset( $_SESSION['cptch_error'] );

    // return $errros.'<strong>TEST</strong>';

    if ("" ==  $_REQUEST['recaptcha_response_field'] ) {    
        return $errors.'<strong>'. __( 'ERROR', 'captcha' ) .'</strong>: '. __( 'Please fill out The Cpatcha.', 'captcha' );
    }

    if ( isset( $_REQUEST['recaptcha_response_field'] ) && verifyCaptcha()) {
        // captcha was matched                      
    } else {
        return $errors.'<strong>'. __( 'ERROR', 'captcha' ) .'</strong>: '. __( 'Please enter a valid CAPTCHA value.', 'captcha' );
    }
    return( $errors );
}




add_action( 'login_form', 'addCaptcha' );
add_filter( 'login_redirect', 'verifyCaptcha', 10, 3 );  
add_filter( 'login_errors', captcha_errors);