Tanksley was treated at Our Lady of Lourdes Medical Center in Camden and released that day. He tried to recoup his medical costs and hired an attorney.
Marlton attorneys Charles H. Nugent and Jeffrey Pooner had been searching for the driver to serve a civil lawsuit.
The attorneys, however, said they were shocked to learn recently that the mysterious driver worked for the same agency that investigated the crash.
Nugent said Tanksley's SUV, which had been going about 55 m.p.h. in Lawnside, was struck with such force from behind that the impact flipped it on its roof.
Afterward, investigators for the law firm could find no trace of the driver.
"It certainly looks suspicious," Nugent said during an interview Monday, a day after the Newark Star-Ledger reported details of the accident. "It was a cover-up."
According to police reports, both vehicles were going south when the crash occurred about 2:30 a.m. Tanksley is listed as one driver, but the other driver was listed as William J. Gillespie, 51, of Clementon.
A bogus Vineland company was the documented owner of the Nissan Altima, an undercover state police vehicle.
Billingham told investigators, "I apparently fell asleep," according to a state police accident report.
Although undercover authorities are permitted to use false identities to protect an investigation, later they must file corrections to reports.
Paul Loriquet, a spokesman for the Attorney General's Office, said he could not comment on whether protocol had been followed. The matter is under investigation, and Loriquet said he could not disclose details.
"We're obviously concerned," Loriquet said.
Nugent said that when his office requested documentation, the state police turned over a two-page report with Gillespie's name.
Tanksley, an actor who appeared on The Cosby Show under the name Clayton Prince, has more than $30,000 in unpaid medical bills.
Neighbors at the Clementon address couldn't recall a William Gillespie.
"They said they never heard of him," Nugent said. "It's like he disappeared into thin air."
Jason Laughlin, spokesman for the Camden County Prosecutor's Office, said the state police sent the case to his office on Oct. 29, 2009. It was noted that Billingham, an 18-year veteran of the state police, is related to Sheriff Charles H. Billingham.
Laughlin said his office consulted with the Attorney General's Office.
"Because of the situation with Sheriff Billingham, we wanted to avoid even the appearance of bias or conflict of interest," Laughlin said.
By January 2010, the case was sent to the Ocean County Prosecutor's Office. Officials there filed a complaint in March of this year. William Billingham was charged with reckless driving and causing bodily injury. He appeared in Lawnside Municipal Court, where, his attorney said, he pleaded not guilty. The attorney declined additional comment.
Meanwhile, Billingham also was suspended from the state police. Acting Maj. Gerald Lewis, a spokesman for the agency, said the case remained under investigation. Lewis said he could not discuss details other than to say that efforts were being made to make sure Tanksley and his insurance company had the proper information.
Nugent said additional reports from the state police include diagrams that refer to the vehicles as the Tanksley Mitsubishi and Billingham Nissan, but that the information had initially been withheld.
Contact staff writer Barbara Boyer at 856-779-3838 or firstname.lastname@example.org.
Inquirer staff writers James Osborne and Darran Simon contributed to this article.