Alcatraz conducted counts at multiple intervals through the day and night. The overnight counts were the ones the escape exploited. Guards walking the cellblock after lights-out were not performing the same kind of check as the morning count. They were performing a welfare check — confirming that prisoners were present, in their bunks, apparently alive. This is a different cognitive task from a formal identification procedure.
A formal identification procedure would involve confirming the prisoner’s face, checking against a known photograph, perhaps addressing the prisoner by name or number and noting a response. A welfare check involves confirming that the shape in the bunk is a person-shaped shape and that it is not in distress. These two tasks activate different levels of scrutiny.
The dummy heads were designed for the welfare check, not the identification procedure. They were not designed to fool a guard who stopped, shone a flashlight directly at the face for ten seconds, and looked carefully. They were designed to fool a guard who swept a flashlight across the bunk from outside the bars, saw a shape with a head-sized object at the top, registered it as “inmate, present, apparently sleeping,” and moved on.
This distinction — between the check that was designed and the check that was actually performed — is what made the escape possible. The men who built the heads understood what they needed to survive, and they built exactly that. They did not need a perfect human likeness. They needed something good enough for the check that would actually happen.