MEMPHIS—Memphis police waited four days after Harvard professor Don C. Wiley’s disappearance to launch a full investigation into explanations other than suicide, possibly losing crucial evidence.

Both Wiley’s sister-in-law and a Memphis police officer familiar with the investigation said the preliminary police inquiry—handled by the police department’s Missing Persons bureau—did not include the forensic tests and area canvassing conducted by Homicide bureau detectives when they took over the case four days later.

Wiley, Harvard’s Loeb professor of biophysics and biochemistry, was last seen after a banquet at the Peabody Hotel in downtown Memphis on midnight Nov. 15. His rental car was found abandoned on a bridge over the Mississippi River four hours later.

Susan Wiley, Wiley’s sister-in-law, said Missing Persons investigators told her the day after the disappearance that they were only actively investigating suicide at that point.

When she urged them to explore other possibilities and dust the abandoned rental car for fingerprints, she said she was told, “Let us do our job.”

“They certainly weren’t beating the bushes,” she said. “I don’t think they did much. I have absolute faith in the people investigating it now.”

Missing Persons is a branch of the Memphis Police Department’s (MPD) general assignment bureau. “[They] seldom get out of the office. [They] make telephone calls and put information in the computer,” the MPD officer said.

The Missing Persons bureau does not do the field work that characterizes the Homicide bureau.

The MPD officer familiar with the investigation said the department’s heightened response and the shift to Homicide were a direct result of pressure from Harvard and St. Jude Children’s Research Hospital, which sponsored the convention Wiley attended Nov. 15.

“It was transferred from [MPD’s Missing Persons bureau] to Homicide because it was a high-profile case,” the officer said.

Susan Wiley said police told her they made the switch because Homicide had more manpower than Missing Persons, and MPD spokesperson Latanya Able said the bureaus frequently worked together.

Able said that the homicide department conducted forensic tests on Wiley’s car when they took over the case. By this time, the car had been handled and removed from the bridge.

Able would not comment on the results of the tests, but Susan Wiley said that police told her they found just two partial fingerprints.

Tests are rarely done at the scene of the crime without signs of foul play, according to the MPD officer. But Susan Wiley said that Sgt. Robert Shemwell, the homicide detective in contact with the family, told her that the car’s missing hubcap and the yet-unexplained streaks of yellow paint on its bumper indicated that, even at first sight, the disappearance was not a clear-cut suicide.

Tennessee Department of Transportation official Bob Parrish said that the car, parked in a construction zone on the Hernando de Soto Bridge, was moved promptly, letting construction work continue the next morning.

A half-inch of rain also fell in Memphis Nov. 19, the day before homicide detectives took over.

According to James Burke, a state-certified private investigator in Boston, any precipitation could have compromised forensic evidence on the bridge and its railings. Wiley would have had to climb over the bridge’s high railings in order to jump off, MPD spokesperson Richard True said.

Within days of taking over the case, homicide detectives also scanned surveillance videos at local stores for evidence of Wiley’s activity after he left the hotel, put up posters with Wiley’s picture and interviewed Peabody employees, conference attendees and others in the area around midnight on Nov. 15.

According to True, the department has assigned three full-time detectives to work exclusively on the Wiley case and can add more as needed.

Able stressed that Wiley is still being investigated as a missing person, not a suicide.

But the MPD officer said, “We probably know where he is right now, but no one wants to believe us. Ninety-nine percent of abandoned cars we find, [the drivers] go in the river.”

Able, who took over responsibility as the MPD spokesperson on the Wiley case yesterday, declined to comment on any of the evidence Susan Wiley says Shemwell discussed with her.

—Daniel K. Rosenheck can be reached at rosenhec@fas.harvard.edu.

—Elisabeth S. Theodore can be reached at theodore@fas.harvard.edu.