Telepathy currently sees things with minds. Change it (or perhaps change only the amulet of ESP, leaving other telepathy the same) so that it sees things with souls instead of minds. Mostly this corresponds with the same monsters (with a few exceptions such as mummies which are animated by the soul of the dead person), but if a monster with a soul is polymorphed into a form that normally doesn’t, it retains its original soul, and shows up as its original form to ESP.

Additionally, ESP shows the spirit of a humanoid with a soul just after you kill it if you’re blind, making some angry or resigned gestures before fading away.