Cases of foreign body ingestion in the forensic literature are mainly described in children or psychiatric patients. Postmortem imaging can detect most foreign bodies, but its sensitivity depends, among other things, on the type of item and its location. In some cases, the ingestion of foreign bodies can remain unnoticed and have serious consequences for the patient. We describe the case of a patient who died in a psychiatric seclusion room with no obvious cause and for whom a forensic autopsy was requested. Further investigations showed the existence of a subdural hematoma associated with a midline shift, secondary to a skull fracture that was considered to be the cause of death. Toxicological analyses identified in blood several drugs, including diazepam (24 ng/mL) and its major metabolite nordazepam (24 ng/mL), propranolol (57 ng/mL), paliperidone (9 ng/mL), and loxapine (620 ng/mL). The forensic autopsy revealed the existence of a gastrointestinal perforation after the ingestion of a plastic teaspoon, which the postmortem CT scan had failed to detect. Although technological advances continue to assist the forensic pathologist in his diagnosis, autopsy still has a leading role in forensic investigations and does not yet seem to be replaceable by imaging techniques alone.