Marcia Clark, the former Los Angeles prosecutor from the O.J. Simpson trial, makes her fiction debut with Guilt by Association, featuring her alter ego, Assistant DA Rachel Knight.

What led you to choose a career in law?

I had wanted to work in the State Department. I spoke four languages, and thought that was something that I could do. But back then [the mid '70s], they had basically just asked me if I could type, which wasn't what I had in mind. I decided to try law school, and from the first couple of months, I knew that I wanted to do criminal law.

How did you transition from courtroom attorney to novelist?

I've wanted to write fiction since I was a little kid, but I wanted to live indoors and wasn't sure I could manage that if I wrote fiction for a living. And then I had kids, and there was no time when I felt comfortable that my writing skills could earn enough. When my kids were grown, and I had an appellate practice, I thought I'd take a shot at this. I saw Tales of the City on television and loved it so much, the writing, the characters, going into another world, and decided that I wanted to share with everybody else the incredible fun, excitement, fulfillment, satisfaction, and camaraderie of being a prosecutor.

How much of Rachel is you?

Rachel's my avatar. She's better than me in every way possible—she's smarter, she's tougher, she's stronger, funnier, prettier, younger. She's flawed—don't get me wrong—she still has me in there, so she has a big mouth, she says the wrong things to the wrong people, she pisses people off, she can be too abrasive, and she can be too direct. At the end of the day, though, she's a good friend, a good-hearted person, who wants to do the right thing, and cares deeply about the victim and justice.

What about Los Angeles makes it a unique setting for your novel?

I've had the privilege of living in a lot of big cities; L.A. is distinct—it's such a sprawl that it's almost an amalgam of different cities. As a result of the geography, the traffic is almost a character in the book. It takes so long to get from point A to point B that people wind up talking about personal stuff in the car. That dynamic changes the way people interact. It's really hard to run into someone that you know here, and that makes for a whole different feeling.