Might you perhaps have some insight intrinsic to this incident?

I like how @Marcia Maynard handles the issue with a potential tenant - basing her decision to rent to them on the tenant's decision as to whether they have, or will, make good with their former landlord and that it was an isolated incident.

I wish more details of the security protocol & horrific incident were given, but how do you protect your MFR investment from being sued over and/or won against something like this and can the same scenario be applied to SFRs?

We look at severity of crime, how long ago, and how many incidents compared to NONE.We look at stable rental history beyond landlord references - how long they have lived at addresses and in the area.  

Detectives spoke with doctors from [MedStar] Washington Hospital Center who advised that [the victim] was most likely not going to survive this incident," officers wrote in court documents.https://wjla.com/news/local/po...

Lived there another 3 years before relocating for work reasons without incident.

Apparently another incident and the dog(s) will be destroyed.  

The claim was under $2K and was for a non-repeatable incident.

Some companies can exercise their own discretion and approve based on how long ago the felony occured, for instance if the possible tenant commited that crime at 18 and is now 42 and has had no other incidents, then they will overlook the felony; but some will autoatically deny if anything shows up.

You'd never be able to prove they did it unless you could find a judge that would summon the tenants cell phones in discovery hoping that one of them was recording "for the Gram" when the incident tool place.