Depends if you are talking about your own internal audit or Concur Audit Service.
Internal Audit, absolutely, you'd create an audit rule that fires each time said Employee submits an expense and it forces it to go through all the steps in the workflow.
Concur Audit Service (The way I build it) also does this, you select a random percentage and all the reports flow through that. But all the system is doing is generating an 'Audit' exception code which prompts audit service. You could use the same code and create an audit rule just for said employee.
Other companies call this the black list but it isn't something I recommend as it isn't very transparent. You can create a query in the processor tab which can review only specified employees Expense reports or a report in cognos.