Someone was murdered in my house, is the landlord required to tell me if they knew?

If you mean that if they knew that someone was murdered there, then it would depend on the law that is effect where the property is located.

Where is the property located?

One example that I found concerning this subject is on the following site. http://www.dca.state.ga.us/housing/H...HANDB-PgNo.pdf

What is below, is a quote from the above site.

Quote:

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Do landlords have to reveal to prospective tenants that a murder occurred in the apartment?

Owners and their agents should respond truthfully if they are asked direct questions about the property's past. Georgia law (O.C.G.A.§ 44-1-16) directs owners or an owner's agent in a real estate transaction to answer truthfully to the best of their knowledge if asked a question concerning the property's prior occupancy by a diseased person, whether the property was the site of a homicide, other felony, suicide, or death by accidental or natural causes. If answering such questions would require disclosure of information that is prohibited from release under state or federal law, the landlord may not answer. No cause of action is created by the failure to disclose such information.

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Again, where is the property located? It's possible that there may be information concerning that available online. But, I can't guarantee that the information is available online.