Final answer:
In suspected poisoning cases, forensic toxicologists must immediately examine the gastric contents to uncover any undigested toxic substances or pills.
Step-by-step explanation:
A forensic toxicologist should request to check the gastric contents of the deceased member of the mafia to determine if poisoning is the cause of the sudden death. In cases of suspected poisoning, examining the gastric content is essential because it may contain undigested pills or residues of a toxic substance that led to the victim's death. The gastric contents can provide vital information about the presence and type of poison, which is crucial for the forensic investigation.