The string of successful procedural series on CBS continue to thrive this season with audiences not showing any signs of tiring of the tried-and-true formulas of such series as "CSI," "NCIS" and the newest entry, "The Mentalist." One other CBS series, "Criminal Minds," is currently enjoying the biggest ratings of its four-year history. Our Jim Halterman talked to co-executive producers/writing team Debra J. Fisher and Erica Messer about the loyal fans, how they got used to the horrors of real-life crime and how an early job on a show about orphans prepared them for the world of procedurals.

Fisher explained that she sees the show's popularity in two parts. "The biggest part of it," she said, "is that our core fans of the show have never left and I truly believe that it's because of the characters on our show... we're not a character-driven show but, honestly, [the audience is] so invested in these characters and this core audience has not left and we're just gaining new people." Secondly, she credits CBS and the audience the network tends to attract. "They have a formula and they have people who love to come in and sit down once a week and, even if they didn't watch the first two seasons, they can come in and sit and jump right into it and catch up." Fisher said there are other series that you can't do the same thing. "Look at 'Lost.' If they lose you in the second season, you're not coming back and I can't imagine them getting new viewers."

Messer likes to think it's the stories they tell on the series that captivates viewers. "We are telling dark stories that people are fascinated with and the stories that we tell are often based on true events and so, in some ways, we're just bringing those stories to life." Messer likened the public's never-ending interest in true crime to an infamous serial killer who is still talked about. "When Jack the Ripper was out there, there were no TV shows about him, obviously, but it was huge in the press and the horror of Jack the Ripper has always fascinated people and he was one of the darkest killers our there and so I think it's just the fascination with the way other people think. It keeps our audience always wanting more."

Fisher also explained that while the writers are conscious of making sure there are some personal elements for the cast members in each episode, there is a fine line they try not to cross. "We always try to have one or two characters and they have a thread going through that episode," she said. "Whether they are going to find something with the victim or the family or this is a case they worked on years ago." But the writers make sure they don't allow the crime of the week to be overshadowed. "If we sprinkle it in, the fans love it but I don't believe they'd want to see that every week at all. They love the case... sometimes we'll do bookends with personal moments, that's enough for most of the audience."

Having been a part of "Criminal Minds" since the beginning of the series, one would think that Fisher and Messer honed their procedural teeth on other hard hitting shows like the two seasons they spent on "Alias." However, the writers learned about television writing when they worked as assistants to the Executive Producers on a series that is about as far removed from "Criminal Minds" as one could imagine. "It sounds like it wouldn't be the same worlds at all," Messer said, "but we always say we were raised at 'Party of Five' and I think it's because we learned so much from the sidelines and you were able to see what the struggles were in the writer's room... it was really invaluable."

The Jennifer Garner action-based series "Alias," was a surprisingly natural bridge for the writing team on their first position as staff writers. Messer explained, "At the heart of that show, in the beginning, it was about a girl struggling with her identity and that is relatable across the board. Certainly it was something that the characters on 'Party of Five' had to deal with so in a lot of ways it came really naturally to transition from being around the Salinger kids to Sidney Bristow's world."

Now that they've spent several years writing about the darker side of crime, has their perception of crime changed? "Four years later, my heart is cold," joked Fisher. "I was very affected by what we would read and write about. To see myself go from the first season to now... there are very few things that effect me that way. Things with children are upsetting but I'm stone cold hard now."

"I kind of equate it to being in medical school where you just stop seeing the blood," Messer offered. "We kind of stopped seeing the crazy and we just became fascinated with the why. Why is this person like this?" One of the scariest explanations for why someone does something can often come without a true motive, the duo discovered. "Truthfully, when we talk to our profilers, sometimes they say it's just because they're sick and there's no logical explanation to it. It's psychology. It's genetic. It's your environment."

One positive Fisher sees in the stories that are told on "Criminal Minds" is the way in which the public can become better educated. "We did a stalking episode and everything in it was telling women what not to do. If someone's stalking you, you have to be very careful when you're in public and you're giving out private information like, to the dry cleaner and what your name is and what your phone number is and what your address is... it's helping people make better choices on basically how to live and people tell us that all the time."

After four season's worth of crime, do Fisher and Messer worry about running out of stories? "The truth of it," Messer said, "is that the real world is such a darker place than anything we write about and there's sadly always an inspiration for a story out there." Of their current season of good guys triumphing over bad guys, Fisher couldn't be happier. "I feel like this season has been a really great season creatively. Every episode I think, this is fantastic. I'm really proud of the work everybody is doing this year. It's been really good."

Besides the usual cases coming up in future episodes (such as an upcoming story written by Fisher and Messer on the kidnapping of a child), there are also some notable guest stars making appearances. "Saturday Night Live" alum Nora Dunn guests in the "Pleasure Is My Business" episode (airing February 25), C. Thomas Howell ("The Outsiders") appears in the "Omnivore" episode (airing March 18) and Cybill Shepherd ("The L Word" "Psych") appears in this week's episode, "Cold Comfort," as the mother of a suspected serial killer.

"Criminal Minds" airs every Wednesday night at 9:00/8:00c on CBS.