Dead players should only be able to mic/chat other dead players so any alive player will not hear/see them. The only way they can Ghost is they have private chat like Skype or etc. or Lan party or you have an addon for private chat or chatbox.

I can still hear other players when they are dead though, it may be because I am the owner?

You still shouldn't hear from them, unless the round just ended and it's in the process of starting a new round. I have the latest Version of Murder gamemode installed on my server and even when I join my server I still can't hear dead players talk or chat, the only time is when I'm in spectate mode that I hear them or see what in the chat.