Don Wiley, 57, fell from the Hernando DeSoto Bridge after a minor car accident there, Shelby County Medical Examiner O.C. Smith said. There were no marks on the body indicating foul play, he said.
Smith said yellow paint marks on Wiley's car door indicated that he may have hit a construction sign. A hub cap also was missing from the right front wheel.
Wiley apparently got out of his car to inspect the damage when he went over the railing of the bridge, where traffic had been reduced to one lane each way because of construction.
The draft from a passing 18-wheeler may have caused Wiley to lose his balance and fall into the river, the medical examiner said.
Authorities initially thought the 57-year-old father of four had committed suicide, but Smith said he ruled out the possibility based on evidence from the car and statements from Wiley's family, who insisted it was unlikely. Police say Wiley had no known financial or domestic problems.
Wiley had been in Memphis for a scientific conference sponsored by St. Jude Children's Research Hospital. He was last seen publicly at a conference banquet Nov. 15, and colleagues said he did not appear distressed or intoxicated.
His rental car was found a day later, abandoned on the bridge with the keys in the ignition and a full gas tank. The hazard lights were not flashing.
The body was discovered Dec. 20 snagged on a tree near a hydroelectric plant at Vidalia, La., about 300 miles south of Memphis. A wallet containing Wiley's identification was found on the body, which was identified through dental records, police said.
Wiley was a professor of biochemistry and biophysics in Harvard University's molecular and cellular biology department. He and another Harvard professor won honors for their work on how the human immune system works, including the Japan Prize two years ago.
Wiley's disappearance had raised concerns about a possible terrorist connection since he had done research on a number of potentially deadly viruses, including Ebola, a highly contagious and lethal fever.
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