A two line email from their agent to yours when he asks is at least polite "Thank you again, the seller still has not made the full determination at this time, Your offer was presented through the channels and we are working on moving it forward" (takes 10 seconds and he can have it in notepad to copy and paste), but I don't think it is criminal or shady (it could be).I will say though that listening to @Bill Gulley would always be a smart choice in my opinion.

Sit down with them and literally exchange criminal checks.

Also, you have people who have invested in safe, and high crime areas, so you can bounce ideas off of them there.For the most part personally, we made sure we secured the building in a way that really deterred criminals, and made sure we do a block by block analysis - learn how to read which blocks were good, and which ones we should stay away from.

Run thorough criminal background checks. 

It all depends on what your lease says.Here is some language in mine that covers criminal activity (however, if no charges were filed, then your situation probably wouldn't apply):11.

She filed a complaint and were summoned to appear; this is normal legal process - it was not a criminal complaint.

After 9 days of him giving me the runaround when asking if funds were received, I only got him to admit he had the money due to my call to the FBI to file a criminal complaint.

My night job is a winged superhero protecting Gotham City from criminals. 

The system I use charges $16 for a credit/criminal and I charge $20.

have you used it and does it do a pretty thorough background check into credit, evictions, criminal, etc?