Landlord Responsibility: Batteries not included – The case

Who’s responsible for smoke detectors?  A fire in a rental property kills five people, the smoke detectors did not work.  The landlord did a routine check at move in a found the detectors were operational. The landlord also had a scheduled maintenance plan for the properties.   The tenants may have disconnected the detectors. Who is liable?

(Excerpt from the Quinlan Landlord Tenant Law Bulletin)