In Trust Me, a new BBC television series, Jodie Whittaker plays a nurse posing as a doctor. The series is written by a physician who worked in a hospital where a fake doctor was caught.

It’s a rare but not unheard of occurrence. In February an 18-year-old in Florida was arrested for operating an illegal medical office and was caught after he performed a physical and gave medical advice to an undercover agent.

Reports of these cases are mostly anecdotal but have definitely happened. As long as there are con artists they are likely to happen again, every once in a long while. Catch Me If You Can, the 2002 Steven Spielberg film is based on Frank Abegnale Jr.’s book of the same name. It’s the story of a teenaged Abegnale’s crime spree as an impostor, including the period in which he fooled one hospital’s staff into believing he was the supervising resident. While posing as a doctor on a Canadian destroyer during the Korean War, Fernando Waldo Demara, known as, The Great Impostor, treated wounded soldiers and even performed surgery.

What motivates these fraudsters is anyone’s guess. To theorize about their motives, you might turn the qualities of what makes a good doctor on their head. Instead of having compassion, these impostors put themselves, not their patients, front and center. Instead of serving their communities, these impostors want to enrich themselves monetarily and/or in the form of the ego boost they get from donning a white coat and being regarded as an authority or someone of high social standing. Or, maybe it’s power they crave. They may believe they can control those around them by posing as a trusted physician. A more generous theory is that these people themselves don’t really know who they are and in a very extreme way, are trying on a new identity. Whoever they are on the inside, they put patients and their ‘colleagues’ at great risk. There’s no denying however, they do make for good villains and anti-heroes in books and movies though.