- You may be looking for the novel.
They were red and iridescent, and used to indicate that a Kaldor android was deactivated.
Aboard Storm Mine 4, Taren Capel had the sandminer robots he controlled place corpse markers on their human victims as a ironic gesture born from Capel's belief in robot superiority. (TV: The Robots of Death)
During one spate of murders in and around Kaldor City, they were forced into the hands of human victims. They were a clue the Fourth Doctor and Leela used to help solve the mystery of the murders. (PROSE: Corpse Marker)