It’s incredible to think that a law enforcement worker might have lied to scores of police officers and firefighters by claiming to have cancer, eliciting sympathy and money and even putting together a false chronicle of her medical odyssey.

But Napa’s own Dannille Vanderpool, a former police dispatcher, stands so accused.

She pleaded not guilty last week to more than a dozen charges that she falsified a diagnosis of ovarian cancer to gain some $50,000 from supporters.

A Napa police investigator said that Vanderpool admitted she does not and did not suffer from cancer. Separately, her defense attorney said that she has a psychological disorder, one that predates by years the fundraisers in her honor.

The 50 grand doesn’t sound like a lot of money by today’s dizzying bail-out standards.

The shocking aspects of this story are that police officers are among the ones who appear to have been taken, and even more so that people may have been burned while acting nobly and generously.

(Full disclosure: The Register reported on Vanderpool’s accounts of her own illness in a sympathetic front-page profile in October, 2007.)

If Vanderpool did what she is accused of, she is not the first. Psychological literature shows a history of people falsely claiming illness — sometimes for material gain, sometimes not — going back for as long as anyone has been keeping track.

The American Psychiatric Association publishes a book that is a bible of sorts for those working at the busy intersection of criminal behavior and mental illness.

The book is known as the DSM, short for the Diagnostic and Statistical Manual of Mental Disorder.

One psychological problem listed in the DSM is factitious disorder. According to the DSM, people with factitious disorder have gone so far as generating scars or encouraging outward symptoms of illness to perpetuate their fraud.

They sometimes go to hospitals in what they know — somewhere inside them — to be a vain search for the physical cause of what ails them.

The three criteria for an FD diagnosis are the feigning or purposeful creation of symptoms of illness; a motivation to assume the role of a sick person; and a lack of external incentives, such as financial gain.

That last factor is the only difference between factitious disorder and a problem more of us have heard of: Malingering. Malingerers are doing it for the money or to avoid work or military service, according to the DSM.

The problem in either case, and this may become a problem for a Napa County Superior Court jury, is that it is awful hard to tell which is which.