AUBURN — An Androscoggin County grand jury considering criminal charges stemming from an October haunted hayride in Mechanic Falls that turned deadly is expected to meet for a rare third month in July.

“We’re continuing to provide all of the evidence necessary to the grand jury to make an informed decision about this very important case,” District Attorney Andrew Robinson, chief prosecutor for Androscoggin County, said Friday.

Robinson began presenting his case, including evidence and witnesses, to the grand jury in May and continued through the first week of June. On Friday, he determined that a third session would be needed to conclude the presentation of the complex case.

“It’s very unusual” for a case to be carried over to three grand jury sessions, Robinson said. This is the first time in the past 15 years that he has found it necessary to seat the same grand jurors more than twice for a single case, he said.

Robinson said his office had reviewed hundreds of pages of investigative reports and hired an expert to review the case for possible criminal action before first presenting it to the grand jury last month. He declined to disclose the names of any people against whom the grand jury is considering returning indictments.

On the night of Oct. 11, a flatbed hay wagon spilled dozens of riders into the woods when the Jeep pulling it down a steep hill jackknifed and slammed into a tree. By the following morning, it was revealed that a 17-year-old girl from Oakland had died and nearly two dozen others were badly hurt, suffering broken bones and head, back and neck injuries.

The ride took place at a Halloween attraction called the Gauntlet at Harvest Hill Farms on Route 26, owned by Peter Bolduc. Investigators said it appeared a mechanical failure led to the rollover, in which Cassidy Charette, a student at Messalonskee High School, died of her injuries. Seriously hurt was Charette’s boyfriend, 16-year-old Connor Garland of Belgrade.

Teams of investigators from state agencies spent weeks probing the cause of the wreck. The Androscoggin County District Attorney’s Office had said initially that it planned to present findings to a grand jury in February, but the office stretched out that time frame for months, largely waiting for a report from a private consultant.

Troopers, motor vehicle inspectors and state fire investigators inspected the 1979 Jeep CJ-5 at a local garage, after executing a search warrant. The vehicle autopsy was aimed at detecting any mechanical failure that might have occurred on the night of the crash. The towing capacity of the Jeep also was a focus of the investigation.

cwilliams@sunjournal.com