Police say Herneisey, 51, a middle school special education teacher in Middletown, Pennsylvania, allegedly conned her school district to give her time off from work because of her feigned illness. She also allegedly accepted money colleagues raised to send her on a free trip to Disney World.
"I think this is something that spiraled out of control and got bigger than she expected. Once you commit a falsehood as big as she did, it's kind of hard to go back on," Detective Robert Appleby of the Lower Swatara Police Department told ABC News in an interview.
Herneisey's alleged web of deceit began as much as a decade ago, police say. According to Appleby, police have records showing she allegedly began claiming she had a brain tumor at least 9 years ago, in order to be granted sick leave.
"She was granted sick bank on numerous occasions over those nine years for the tumor and it might go back as long as 16 years," Appleby said.
"She is very depressed," said her lawyer, Terrence McGowan, in an interview with ABC News. He said he believes the whole web of lies began when Herneisey, suffering from years of clinical depression, began to use the cancer ruse as a way to stay home from work. McGowan said he did not yet know what plea he would enter on his client's behalf.
"That's what started this whole thing and it got out of control. It's not like she was at the beach on her days off, she was home and in bed with the lights off," McGowan said.
Herneisey, took things a step further last year, police say, when she allegedly submitted a letter to the Middletown School District claiming she now had an inoperable form of brain cancer and needed eight weeks off to undergo chemotherapy.
The school district and her colleagues rallied around the 25-year veteran teacher and, according to Appleby, they sent her story to the Make a Wish Foundation in hopes Herneisey and her family would be treated to something special.
"Her application was denied because the Make a Wish Foundation found that her medical documents were not forthcoming," Appleby said.
The rejection might have tipped people off to inconsistencies in Herneisey's story -- but instead, it only pushed her fellow teachers to try harder.
"Her coworkers then raised funds and sent her and her family on an all-expenses-paid trip to Disney World,' Appleby said.
Appleby says it was a testament to the reputation Herneisey had as an educator.
"She was a great teacher," he said.
In addition to her nominations for teacher of the year, the Middletown District's website says she received a local award for educational leadership.
"Her peers always enjoyed working with her, and students loved her as a teacher," Middletown Area School District Superintendent Richard Weinstein told ABC affiliate WHTM-TV in an interview.
Herneisey's claim to be fighting cancer came under suspicion when, according to police, the school district began to notice she wasn't actually showing any signs of inoperable cancer or chemotherapy, and rumors began to swirl that it was all made up.