Final answer:
A stiff and warm dead body indicates rigor mortis, a post-mortem process beginning within 2-6 hours after death, which can help estimate the time of death.
Step-by-step explanation:
A dead body that is stiff and warm which would indicate death less than 8 hours ago is exhibiting signs of rigor mortis. This physiological process begins within 2 to 6 hours after death and is characterized by the stiffening of the muscles as a result of chemical changes within muscle tissue. Rigor mortis can be used as a tool by forensic investigators to help determine the time of death. It's important to differentiate rigor mortis from other conditions such as hypothermia, which is a dangerous decrease in core body temperature, or heat-related conditions that can also be fatal but are unrelated to the post-mortem process described here.