When an investor owns and manages apartments he or she often has to make tough decisions.
Here's an example of one:

Barry and Terri, husband and wife, are tenants in a four unit apartment building. They have a stormy relationship that one evening erupts into a violent domestic dispute. Terri calls police. The incident isn't quite exciting enough to be included in an episode of "Cops", but Barry is arrested and charged with domestic violence assault.

Directly after the arrest the couple separate and Barry lives elsewhere.

The next day the landlord serves Terri with an eviction notice for violating the quiet occupancy clause in the lease. This landlord gets more grey hair, because Barry, hoping to win his way back into Terri's heart makes a return. He comes screaming into the landlord's office demanding the eviction be cancelled. He says it was his entire fault, he was that one who was arrested and Terri shouldn't be punished for his bad behavior.

What would you do in this situation?

The landlord's best action is to calmly explain to Barry that owner/manager had nothing to do with the disturbance. When the lease was signed Barry and Terri had a joint responsibility to abide by the rules and the law. Either party is responsible for the other party.

This is true as a joint and several liability and in relationship to community property law.

As landlord you could not evict Terri if she still qualifies for the apartment based on her own income. You can determine that from the information on their rental application.

Since the landlord knows that Barry and Terri have a volatile relationship there is a good possibility Barry could return in a rage and, in trying to reach Terri, attack another tenant. In such a circumstance if someone other than Terri were to be hurt, the landlord would be liable, since he or she knew about the continuing problem. In situations such as this management typically will evict the entire household when domestic violence occurs.

As I have written before, "Nobody Loves a Landlord!"