A 2020 scientific study examined diatoms—microscopic algae—found embedded in the bills. The study’s authors argued that the diatom species present on the bills were consistent with the bills having entered the river system in spring, months after the November 1971 hijacking, rather than shortly after the jump. This finding, if accurate, suggests the bills did not go into the water immediately—but it does not establish how or by whom they were introduced.
The FBI’s own specialists noted that the bills were found in a location that would not be easily predicted as a natural accumulation point for material originating from the suspected jump zone upstream. Some researchers have speculated that the bills ended up at Tena Bar because the Columbia River’s complex current patterns and the shifting of sandbars during floods could move material in unpredictable ways. Others have argued that the deposit is inconsistent with natural river transport over years.
None of these analyses produced a definitive conclusion. The Tena Bar bills remain the only physical evidence recovered from the crime scene or its aftermath—other than the items left on the plane—that can be confirmed as part of the D.B. Cooper case. And they remain deeply ambiguous.
What can be said with confidence:
The bills are real. The serial numbers match the recorded ransom. The packet arrangement was consistent with how the bills were packaged before delivery in 1971. And $5,800 worth of a $200,000 ransom was found in the sand of a Columbia River beach eight years and nearly three months after the hijacking.