Sorting out liability for the I-95 bus crash that injured dozens of Philadelphia schoolchildren and adults Monday morning will likely involve a painstaking accident reconstruction, and often such investigations produce unexpected outcomes.

Such was the case in 2006, when a bus carrying children from the Norris Square Day Camp in Philadelphia overturned on the northbound lanes of I-95 during the return from a field trip to the Baltimore Aquarium.

As a result of the crash, one of the schoolchildren, then 8-year-old Deneik Brownlee, suffered a crushed hand that later had to be amputated. Police later determined at the outset that the driver of the school bus, who was 18 years old, was on a cellphone and under the federal age limit for commercial drivers on trips across state lines. But James Ronca, Brownlee's lawyer, said an accident investigation soon revealed that the bus was forced out of its lane by a commercial truck that had swerved into it.

Eventually, both the bus line and the truck driver settled with Brownlee's lawyers.

Ronca's law firm, Anapol Weiss, created an animation of the 2006 crash to better argue its case.

Ronca said that, judging from the photos of Monday's crash, it appeared that the driver of the bus had overcompensated, possibly to avoid a collision with another vehicle.

"The driver probably oversteered and the bus turned over," said Ronca. "You can't tell what happened. He may have been the best driver in the world or not known how to address the situation and overreacted."

On Monday, 26 C.W. Henry School eighth-grade students and their chaperones were on a class trip to Washington at 9:30 a.m. when their bus, operated by the Werner Coach bus line of Phoenixville, was clipped by another vehicle and overturned in a southbound lane, midway between Wilmington and Baltimore.

Twenty-nine people were injured, two critically, authorities said. The accident occurred when the driver of a Honda Civic lost control, veered across lanes of traffic, hitting the front of the bus.

Whoever is determined to be responsible, accidents of this sort have the potential to quickly exhaust the liability coverage carried by the driver of the car, if the driver is responsible, said personal injury lawyer Evan Aidman of Narberth.

"This is why you never, ever want to be in an accident with a SEPTA bus; you end up getting sued by 30 or 40 passengers," he said. "The key question is who was at fault, one driver, or both, or maybe even a third party," he said.

Parents of children injured in the crash might have the option of recovering from their own insurers, in cases where the responsible party doesn't have enough coverage, or if their auto policies carry underinsured motorist coverage, Aidman said.

The Philadelphia school district itself has limited immunity, and awards against it are capped by state law. That is why a Bucks County judge, ruling in 2011, reduced a $14 million jury award to Ashley Zauflik for injuries she sustained when she was run over by a Pennsbury High School bus, to the state cap of  $500,000.

Zauflik was 17 when she was crushed beneath a runaway school district bus on Jan. 12, 2007, suffering pelvic and leg injuries requiring the amputation of her left leg just above the knee. The bus driver who caused the accident had stepped on the accelerator when he thought he was stepping on the brake. In slashing the jury award, Bucks County Court Judge Robert Mellon said the result was "unfair and unjust" but that the law left him no choice. Zauflik appealed the trial court decision, but the cap was upheld by the state Supreme Court.

The debate over governmental immunity in Pennsylvania goes back to the early 1970s, when the state Supreme Court, ruling in the case of a 15-year-old boy who lost an arm in an industrial shredder used in an upholstery class, overturned long-standing immunity for school districts and municipalities. State lawmakers responded by enacting legislation restricting liability to $500,000 per accident.

Ronca believes the school district's limited immunity likely will be a substantial protection for the school district in Monday's bus accident.

"I don't think you can get by immunity by saying they did a bad job in selecting the bus company," he said.