One expert, University of Texas psychology professor James Pennebaker, compared some of their words to those in the harrowing diary of Anne Frank, the Jewish teenager who hid from the Nazis during the Second World War.
Prof Pennebaker, a specialist in the use of writing to help cope with traumatic experiences, said: “Anne Frank lived in an insane world, but her family was remarkably normal. This is the exact opposite.”
He described the ordeal of the 13 Turpin children at their house in Perris, California, as “the most horrific story imaginable” and questioned why their parents allowed them to chronicle their captivity and “basically stockpile evidence of their crimes”. But he said writing may have kept the children sane.
David Turpin, 57, and his wife Louise, 49, have denied torture, child endangerment, false imprisonment and sex abuse charges.
They were arrested after a 17-year-old daughter broke free and raised the alarm.
Riverside County district attorney Mike Hestrin said the parents were “depraved” and the children’s journals would “provide strong evidence of what occurred in that home for the coming court case”.
Neighbours said they had joked that the Turpins were “like vampires” from the Twilight series. “They only came out at night and were really, really pale,” said Andria Valdez.
Kimberly Milligan, 50, said: “Why didn’t we ever see the kids? In hindsight, we would never have thought this, but there were red flags.”