When landlords did not have access to credit reports or criminal background checks like they do now, then charging a half-month's rent seemed fair as they could do what you could not.  

Security deposit plus move-in fees cannot exceed the amount of the first full month’s rentNon-refundable move-in fees are limited to only tenant screening reports, criminal background checks, credit reports, and cleaning fees.Total non-refundable move-in fees are limited to 10% of the first full month’s rentPayment Plans Required –Landlords must allow an installment plan to pay a security deposit, a pet deposit, move-in fees, and last month’s rent.

Credit score disqualification, insufficient work history or income, criminal record, etc.

If the previous address is close, march into the court house and look up the criminal and civil filings under the applicant's name.

In talking to the tenant she wouldn't tell me his last name - long story short he was trying to hide his background (multiple criminal, evictions, 5 owi's, etc).  

Example from my last real AD.HOUSE FOR RENT3BR2BAmore infomore infoI WILL ONLY RESPOND IF YOU LEAVE A REAL PHONE NUMBER$50.00 non-refundable application feeTypical Qualifications: 600+ Credit Score| No judgements | No evictions| No criminal background | No smokers| No delinquencies |2 pay stubs| whateverElseIRequire ------------------2) I do this to help reduce the amount of callers that will not qualify.3) If you decide to screen over the phone I ask.

I've looked at tenant screening, mysmartmove, turbotenant, rentprep.It's all a bit overwhelming - I think I want it all - credit, background, eviction, and criminal.  

It could possibly be criminal. 

I would immediately talk to a very good criminal defense attorney and get some advice. 

You can also go to public state records available free online and search their criminal history.