I regret that I cannot discuss him with you. If you miss an employee, don't be afraid to say so. If he claimed to be a General Manager and worked as a waiter, you can correct the statement. Use common sense. Never volunteer personal information about the employee, such as address, telephone number, social security number.
Some firms require a copy of a signed release before giving a reference.
A copy of the person's resume can be faxed to you for the sake of confirmation. Never volunteer suspicions or give information about problems which are not documented. Make it very clear to the person receiving the reference that this is priveleged information which is not to be shared with the employee. This is always an assumption, but confirming it is a good idea. Never lie in the person's favor to give him a chance or, worse, to get him employed so that you can quit worrying about workman's comp.