On 29 December 1980, three people near Dayton, Texas reported encountering a large diamond-shaped object and later described symptoms consistent with radiation illness.

Cash-Landrum matters because it is a rare physical-effect case with reported radiation symptoms and a named investigation.
Documented
Three witnesses reported a large diamond-shaped object
Documented
The witnesses reported symptoms consistent with radiation illness
Documented
The case was investigated by John Schuessler
Debated
The object identity
Debated
Whether the reported symptoms were caused by radiation
Unverified
Extraterrestrial origin
Sources are kept in separate layers: official and contemporary material is documented; secondary UFO literature is treated as debated, not as primary evidence.
Documented source.
Secondary / debated material.