gistfile1.php

<?php
/**
 * Check for parent and sub categories
 *
 * @param int $id
 * @return bool
 */
function ja_is_category_deep( $id = '' ) {
	if ( !is_category() || empty( $id ) )
		return false;

	$category = get_category( get_query_var('cat') );

	if ( $category->term_id == $id || $category->parent  == $id ) {
		return true;
	} else {
		return false;
	}
}