Trooper Corey Monthei, a state police spokesman, said Tuesday that investigators had concluded that McCarthy, "had no intention of avoiding responsibility" when he left the scene and showed no signs of alcohol impairment.
"There's no reason to dispute that he was anything but confused, suffering from an illness," Monthei said, adding that privacy laws prevented him from elaborating.
He said McCarthy, who was on patrol in his 2008 Crown Victoria police vehicle, did not know he had hit the other vehicle. He returned after the other driver called 911, not realizing that he was responding to a crash he had caused, Monthei said. When state police arrived about 20 minutes later, McCarthy was at the scene and "cooperated fully," Monthei said.
Allan F. Falcoff, chairman of the Kennett Township board of supervisors, said McCarthy, whom he described as "a valuable asset," is on sick leave.
"We're waiting to hear from his doctor about what happened," Falcoff said of the "low-speed" collision. "Then we'll go from there."
According to the police report, both drivers were wearing seatbelts. Monthei described the damage to both vehicles as minor.
He said in cases like McCarthy's, where no criminal conduct has occurred, sometimes PennDot may take action, such as requiring a driving test or suspending a license.
Falcoff said if it turns out that McCarthy is unable to drive, the township will explore ways in which he could keep his position.
For the past four years, McCarthy, a well-known presence in the township of approximately 7,500 residents, has served as a one-man department, acting as chief, patrol officer, traffic cop, lead detective, and chief arbiter.
"He's probably most valuable . . . in what I call his role as chaplain," said Falcoff. "He ends up settling a lot of disputes that might have escalated; he just has a way with people."
Before working for Kennett Township, McCarthy was a long time officer with the Kennett Square force.
McCarthy joined the Kennett Square force as a patrolman in 1973 and became the borough's chief in 1988. He continued in that position until a contentious parting that culminated with his resignation in September 2007 - and litigation over back pay McCarthy said he was owed.The federal case was dismissed in May 2010 "without cost to either party," according to court records.
Contact staff writer Kathleen Brady Shea at 610-696-3815, firstname.lastname@example.org, or @brandywinebits on Twitter. Read her blog, "Chester County Inbox," at www.philly.com/chescoinbox.