What Makes Tess Tick

International bestselling crime author Tess Gerritsen drew a full house despite the early start on Saturday at Harrogate Crime Festival. Interviewer Dame Jenny Murray set the scene by confessing that reading The Surgeon in her London flat was the scariest night of her life, to a murmur of agreement from the crowd. “My son is at college,” Gerritsen told the audience, “and his roommate read one of my books and said to him, ‘Dude, your mom’s sick’.”

Gerritsen credited her love of grisly crime and her gruesome imagination to her Chinese parents: "My mother learned English through watching horror films. Every Sunday we'd go to the movies and watch one. I was only about five years old. I learnt from films that the scariest part of the movie is before the monster pops out. It taught me about storytelling - you don't need a lot of dialogue in horror films - but it also taught me that being terrified is the height of entertainment."

Ironically, Gerritsen's mother told her daughter her books "aren't scary enough. My mother has the most hair-raising ghost stories from China. I remember saying to her 'well, I've never seen a ghost.' She said to me 'America is too young for ghosts'."

Gerritsen trained as a doctor and only started writing after she had her children. "Like a lot of writers, I knew I was a writer at about seven years old." Being a doctor allowed her to gather material for her future works: "I learnt how doctors think, how labs function - the nitty gritty of hospitals." She said she often goes back into the autopsy room to refresh her memory and keep it ticking.

When asked by Dame Jenny why most of her victims are women, Gerritsen replied that she hosted a reader panel of mostly females, who said that they love serial killer books where the victims are women. "Women want to imagine themselves as victims; we like to read what we fear most, and the idea that it could happen to us makes it more frightening."

Fans will be able to see Gerritsen's female detective duo Jane Rizzoli and Maura Isles on the box later this year on the Alibi channel - news which provoked a ripple of excitement from the audience. The Rizzoli and Isles debut in America opened to the highest ratings on cable TV ever. Gerritsen admitted to watching the show every week at home, despite the fact that casting directors decided that plain, normal Rizzoli would be played by 6' ex-model Angie Harmon, much to the audience's audible outrage. Gerritsen confessed that she hadn't much hope for Rizzoli when she first introduced her, in fact she planned to kill her off pretty quickly, but Rizzoli "refused to go".

Gerritsen is probably quite relieved that she decided to save her star detective, given that she has sold 20 million books worldwide. One audience member questioned what she thought she'd have done had her mother chosen to learn English through Hollywood musicals. Gerritsen evidently hadn't considered this before, and was lost for words. Now there's a thought.