内容摘要："We are committed to preserving and celebrating this tradition for generations to come."

"We are committed to preserving and celebrating this tradition for generations to come."

"The most important thing was to find a non-destructive, portable instrument that could tell us if it was a poisonous book or not," she says.She rule out X-ray technology because of the fragile nature of the books being examined and instead looked to the geology department.

They had a spectrometer - a device that measures the distribution of different wavelengths of light - for detecting minerals in rocks."Minerals and pigments are very similar," says Dr Gil, "so I borrowed the instrument and started looking for emerald green in books."She tested hundreds of books and then realised she was looking at a breakthrough.

"I realised there was a distinctive pattern to the toxic ones. It was a 'eureka' moment. I realised it was something that no one had seen before."The next task was to speak to the physics department to build their own prototype.

Dr Graham Bruce, senior research laboratory manager explains how it works.

"It shines light on the book and measures the amount of light which shines back," he says.Hardin pleaded guilty to first-degree murder after fatally shooting 59-year-old James Appleton in 2017. He was given a 30 year prison sentence.

Mr Appleton worked in the city's water department. He was shot and killed while speaking to his brother-in-law, then-Gateway Mayor Andrew Tillman, on 23 February 2017.While serving time for Mr Appleton's murder, DNA evidence emerged linking Hardin to the long unsolved rape of Amy Harrison at Frank Tillery Elementary School in Rogers, Arkansas, in November 1997.

Hardin pleaded guilty, and received a sentence of 50 years.Before becoming Gateway's police chief, Hardin served as an officer at the Eureka Springs Police Department.