Drugs or Herbs That Simulate Death Symptoms

by Kymberly Dunning
(Springfield, Oregon, USA)

I'm writing a novel. One character appears dead. The MTs and detectives are convinced. When the coroner arrives to pronounce the victim dead he discovers a trace of a heartbeat and respiration that the others missed. He looked deeper into time of death because the low body temp did not decrease as time passed.

Is this possible and what could be the possible drug or herb?