Judge Carolyn T. Carluccio sentenced Searfoss, 42, of Coatesville, to six to 23 months in prison after he pleaded guilty to involuntary manslaughter and driving under the influence.
His plea was part of a deal that allowed the District Attorney's Office to avoid a trial in which prosecutors would have had to prove that Williams' death was caused by Searfoss, rather than by mechanical problems that plagued Lincoln Town Cars such as the 1997 model Williams, who lived in Philadelphia, drove that day.
Searfoss initially faced charges including a felony count of homicide by vehicle while driving under the influence.
The trooper was off-duty on May 18, 2012, when he attended a Bucks County charity golf outing held in memory of a victim of drunk driving. At that event, authorities said, he drank enough to have a blood-alcohol level of 0.188 percent - more than twice the threshold for driving while intoxicated.
About 9:55 p.m., Searfoss drove his Toyota pickup truck onto the westbound lanes of the Pennsylvania Turnpike at Willow Grove, reaching a speed of about 71 m.p.h. After entering the roadway, the truck crashed into the rear of Williams' car, which had just suffered a major engine failure and was traveling about 11 m.p.h. in the left lane.
Investigators said the impact caused a fuel leak, which sparked a fire. An autopsy determined Williams died of blunt-force injuries, burns, and smoke inhalation.
It would have been a challenge for prosecutors to prove in a trial that the events leading to Williams' death were caused by Searfoss' driving rather than by the Town Car's mechanical issues, Deputy District Attorney Samantha Cauffman said.
The plea deal was not ideal, she said after the court session. But it allowed Williams' family to hear Searfoss take some responsibility, and it gave him a jail sentence, she said.
"It is the best result for all parties involved," Cauffman said.
The victim's relatives agreed it might have been the best they could do, but they still were disappointed with the sentence.
"We're not here for revenge, but it just seems light," cousin Gwendolyn Kydd said.
Defense lawyer Christian Hoey said his client was extremely remorseful.
"This is a devastating event for him," Hoey said. "It will always be a devastating event."
Searfoss, who was suspended after the accident, will be eligible for parole six months into his prison term, which is set to begin March 17.