It's called a background check, and it's done by all reputable employers in the US.  All you need is a SSN, and it will tell you their name, any aliases that they might have used, criminal information, and probably even tells what city and hospitol they were born in.  Reputable employers use a service and pay a monthly fee, or a one time fee for unlimited access depending on the firm they use and the size of the company using it.  I don't think anyone is going to just send you a birth cirtificate though.  It would then be easy for someone to steal their identity.  Of course anyone hired by a company for a position in Human Resources should know this, and if they don't, probably won't be employed for very long.  So I guess their isn't any reason to worry about it.  If you are truely legit, I apologize for all implications, but I seriously doubt that an apology is due.  Go try to cheat elsewhere and leave these people that work hard for their money alone.