Bones found at Point Reyes approximately eight months after the escape were buried by authorities under the name “John Bones Doe.” When forensic technology allowed DNA testing years later, comparison with samples from Alfred Anglin — a deceased Anglin brother — produced a negative result. The bones did not belong to anyone connected to the escape.
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## The Alcatraz Physical Environment: Currents and Cold
The FBI’s initial assessment of the escape was that the men had almost certainly drowned. This assessment was based on what was known about the bay’s physical environment: the water temperature, the tidal currents, and the distance involved.
San Francisco Bay at night in June maintains water temperatures typically in the low-to-mid fifties Fahrenheit. At those temperatures, an unprotected person in the water will begin to lose core temperature (hypothermia) within roughly thirty minutes to an hour, depending on physical condition, body composition, and activity level. Vigorous swimming generates body heat but also increases the rate of heat loss from the skin.
The tidal currents in the bay are determined by the twice-daily cycle of ocean water flowing in and out through the Golden Gate. At certain phases of the tidal cycle, the current runs strongly outward through the Golden Gate toward the Pacific; at other phases, it runs inward and distributes more gently within the bay. The window in which a person or raft launched from Alcatraz’s northeastern shore could have been carried toward Angel Island rather than toward the open ocean was time-dependent and narrow.
The FBI concluded that the odds were negligible. The Army Corps of Engineers, which had studied the bay’s current patterns independently, produced models that supported the conclusion: in most launch scenarios from Alcatraz, the prevailing currents would carry a raft or swimmer toward the Golden Gate rather than toward the shoreline.