Douglass states that mr. gore’s crime “was not even submitted to judicial investigation.” why?

This is in reference to when Gore shoots Demby, a slave who does not answer his call. 

Gore explains his actions by saying that Demby was a bad example for the other slaves. Had he not punished Demby for ignoring him, Gore argues, other slaves might follow suit.

For this reason, and for the reason that slaves were considered property (not people), Gore is not investigated for Demby's death. In fact, Gore is admired for his ability to oversee the slaves.