You only need to prove your case to 51%, not "beyond all reasonable doubt" like a criminal case.

@Robert Ablorh If the collections were medical and closed, and their current credit, criminal, and eviction histories as well as their rental references are good they sound like a decent pick to me.  

On background/credit search, they both have good credit history but they both also have criminal background.

Cheryl Hi Cheryl,First of all, disturbing someone's quiet enjoyment is not a criminal offense.  

You are correct about Baltimore and other areas in that the landlord is responsible for screening the prospective tenant for criminal record, sex offender, etc...

They (married couple with kids)  submitted their application online which is our normal process, paid the application fee and all the reports (credit, criminal, eviction) look stellar, plus good income with a job at our big hospital in town.

Before you even get into a discussion about the legitimacy of their emotional support animal see if they pass the other basic screening requirements (income, evictions, criminal background, etc..)If they pass those than I would ask for documentation similar to what @Matthew Paul mentioned.

Aside from credit, be sure to look at a nationwide eviction report and nationwide criminal report.  

You always need to run a background check on the individual applying as well, especially a criminal background check.

You also need to know if either has been evicted or has a criminal record.