Checking for existence for a field on an an entity_metadata_wrapper
Simply call the PHP function isset():

$headshot = array();
if (isset($item_wrapper-&gt;field_contributor-&gt;field_contrib_headshot)) {
  $headshot = $item_wrapper-&gt;field_contributor-&gt;field_contrib_headshot-&gt;value();
}


EntityStructureWrapper implements the __isset() function according the principe of Overloading.