"when" condition with simple: expression for list

There is a List<Map<String,Object>> object in my exchange in body. How can I query of the existence of the 'error' item in the map? This did not work:

<camel:simple>${body.get(0).error}</camel:simple>
<camel:simple>${body[0].error}</camel:simple>
<camel:simple>${body[0].error}</camel:simple>
<camel:simple>${body[0.error]}</camel:simple>