Memphis medical authorities announced yesterday that the death of Harvard biochemistry professor Don C. Wiley was accidental, and not a suicide, as police had previously speculated.

Authorities ruled that Wiley fell off the Hernando de Soto Bridge unintentionally—perhaps under the influence of alcohol or as the result of a little-understood seizure disorder—and officially closed the investigation into his death.

“The medical examiner’s ruling is always the final ruling, and there will be no further investigation,” Memphis Police Inspector J.D. King said yesterday.

Wiley vanished after attending a conference at the Peabody Hotel on Nov. 15. He was last seen around midnight, and his abandoned rental car was reported to police almost four hours later.

Wiley’s body was found 320 miles downstream in the Mississippi River on Dec. 20.

According to Memphis Health Department spokesperson Brenda Ward, the medical examiner hypothesized that Wiley pulled over his car on the bridge to inspect damage from two minor driving accidents—at which point gusty winds could have blown him off the bridge.

According to the medical examiner’s report, Wiley’s broken chest and a missing button on his Giorgio Armani shirt indicated that he hit a support beam on the way down. Past suicide attempts on the bridge have always cleared the support beams, leading the medical examiner to the conclusion that Wiley’s fall was accidental.

Before Wiley’s body was found, however, Memphis Police Lt. Richard True had said that due to the bridge’s 43-inch guardrail, it was “extremely difficult to fall off accidentally.”

“We’ve had that in the past,” True said when the department was investigating Wiley’s disappearance. “But you’d have to climb up over the railings.”

But Ward said yesterday that standing on the 4-inch curb, the top of the rail would have only reached the 6’3” Wiley’s mid-thigh, making it possible for the winds generated by passing 18-wheelers to have blown him off.

Any forensic evidence on the bridge that could have showed where or how Wiley fell off may have been destroyed by the half-inch of rain that fell in Memphis on Nov. 19, according to Boston private investigator James Burke.

Memphis police did not put their specialized homicide investigation team, which would have been looking for such forensic evidence, on the case until Nov. 20.

Medical and police officials still have no idea why Wiley did not go directly to his father’s house as he intended, nor do they know where he was between the time he left the Peabody at midnight and 3:45 a.m., when his abandoned rental car was reported to police, Ward said yesterday.

“Where he went between [the Peabody and the bridge] is just a guess. He could have walked down Beale Street,” Ward said yesterday.

Why Wiley was on the bridge at all also remains a mystery. His father’s house, where he was staying, is in the opposite direction of the bridge from the hotel.