Utah- Need some information

My friend who lives in Salt Lake has had an ongoing problem with their neighbors and their drug problem. My friend witnessed some kind of drug rip and shooting the other night and he is now in fear of possible retaliation due to helping law enforcement locating possible suspects from the crime. He was asking me about he law regarding the protection of his home and family. I know the current laws in Florida but am unfamiliar with the laws of Utah. I've read some articles online and understand there is a law that protects a home owner from civil and criminal prosecution if the use of force is justified, however is the law similar to the castle doctrine or are you a duty to retreat state? Any help would be greatly appreciated.
JB