Whether the admission of investigator testimony via Skype, pre-death victim photos, and denial of mistrial constitute harmless error or violate due process rights

QUESTION(S) PRESENTED 1: was allowing investigator to testify via Skype video messenger Harmless Error? 2: Was statement to investigators freely and voluntarily given? 3: Was admission of pre-death photos of victims harmless error? 4: Was motion for a mistrial and impanel a new jury in error of trial judge when two witnesses were talking abottt the case in arm's length of jury?