PW: There seems to be a lot of relationship activity in A Cold Heart. Is there a formula that you follow for balancing personal with professional involvements as you construct your plots?

Jonathan Kellerman: I've never had a formula. I've never written commercially. My first novel was When the Bough Breaks. Nobody wanted to buy it—the subject matter was seen as too difficult—then it became a word-of-mouth bestseller, and every book's been a bestseller since. I try to tell a great story and characterize well. I try to write the kind of books that I would like to read. I go from book to book, really, and the balance [of those elements] depends upon the story. There are books within the series where there's less of that, but I like to involve the characters to some extent.

When you're writing a series, you have a choice. Do you do what Agatha Christie did, which is essentially to create a static character, Poirot, who never changes, who's really a vehicle for solving a puzzle? I prefer to write a character who evolves, who undergoes life changes, because it's more fun for me to write that, it's more interesting. I write to please myself and hope that someone else likes it. In the last couple of books, Delaware has undergone a little bit of life change, because that's the way it happened, it seemed natural. But I never set out to say, "Gee, I'm going to write a book with [these kinds of] relationships." The story tells itself once you plan it out properly.

PW: You're obviously well informed about LAPD procedure. How did this come about?

JK: I can't reveal my sources. But first of all, when I was a working psychologist, my work brought me in contact with police, because I dealt with children, and sometimes children enter the legal system. We dealt with homicide, suicide and abuse. I was an expert witness in court, so I had court experience. Over the years you meet people. I have friends who are policemen. I have a buddy who's a veteran homicide detective, and I asked him, "Why do you like to read these crime novels?" And he said, "Because he gets the bad guy 100% of the time." I just spoke to a bunch of private detectives, who'd asked me to speak, so I talked to 50 private eyes. There's always opportunities to meet people, and if you're respectful and you're a good listener, there are all sorts of ways to pick up information. But I have my sources. I wrote a book called Monster, where I managed to get into a state hospital for the criminally insane. I've gotten into prisons. There are just ways of doing it.

PW: Is the villain of A Cold Heart based on an actual case in L.A.?

JK: No. I never write about reality. Because I was trained as a psychologist, I was always bound by confidentiality. So I could never write about patients. I didn't want to. I think it made me a better writer because I was forced to invent. All this stuff comes out of my head. What my psychological training and contacts do is hopefully to give [my writing] a feeling of authenticity, The fun of writing fiction is making stuff up. I've written nonfiction books, I've done a lot of scientific writing where you're very tied to facts and documentation, which is an art in and of itself. What I love about being a novelist is letting my imagination go.

PW: Det. Petra Connor seems to get a lot of play in this novel. Do you plan to continue with her in the Delaware series?

JK: She came in as a bit player in a book I wrote called Survival of the Fittest. I liked her so much that I wrote a stand-alone book called Billy Straight in which she was the star. Since then, I've brought her back because I like her. As a matter of fact, I'm writing a novel right now where she is the main character. The next Delaware book that I'm writing, she's not in, but the one after that she'll be the main character.