The determination of the cause of death can be difficult in the following three circumstances:
1. When the body of the victim (dead person) has been damaged after the death. It includes the damage from fire, mutilation, crushing and immersion in strong chemicals.
2. When the dead remains (skeletal) is recovered a long time after the person died, so that no signs are left of the fatal injury.
3. When the person died because of poisoning of trace chemicals that cannot be detected in such small amounts.