How to get a resource user from current state of Workflow?

I need to get a resource participant with started an task in workflow. I can get the taskname, the status of task, the timestamp of start task.
I try to use the method getCompleteCaseLog(<caseid>,<handle>);
However I don't have sucess and the method return:
DefaultWorklist by originator of the started task.
Wich method its possible make this?
i'll be grateful for the help!