Whether the Sixth Circuit or the Eighth Circuit made the correct ruling regarding denial of due process and fair trial concerning the use of a police officers as experts outside of their expertise as law enforcement?

QUESTION(S) PRESENTED WHETHER THE SIXTH CIRCUIT OR THE EIGHTH CIRCUIT MADE THE CORRECT RULING REGARDING DENIAL OF DUE PROCESS AND FAIR TRIAL CONCERNING THE USE OF A POLICE OFFICERS AS EXPERTS OUTSIDE OF THEIR EXPERTISE AS LAW ENFORCEMENT? WHETHER THE PETITIONER WAS DENIED DUE PROCESS WHEN HE WAS DENIED A CERTIFICATE OF APPEALIBLITY REGARDING THE POLICE EXPERT ISSUE AND HIS OTHER ISSUES AS A PRO SE PETITIONER?