dr. kay scarpetta, the main character in 19 of her novels, including the latest one, "red mist." >> whencarpetta is in charge, you are going to be fine. and when she leaves the scene, then it's not safe anymore. >> reporter: how did you come up with her? is she you? >> no, because i dropped chemistry. i practically blew up the lab in college. >> reporter: i confidence, her sense that you're safe with her? >> i think that some of that is me. but there are things about her that are wishful thinking on my part. she's a doctor, she's a lawyer, she's a radiology expert. she does these things for real. i simply write about them. you want to be so good that you have a tight pattern right there. >> reporter: and that's why we're here, not far from the body farm, at the national forensic academy in oak ridge, tennessee. a premiere training ground for forensic investigators from around the country,y cornwell is a major benefactor and a perpetual student. we donned protective gear to take a close look at how blood spatter evidence is analyzed. >> you can tell when someone stomps on a body or hits s

dr. kay scarpetta, a modern heroine. >> i created scarpetta's world. but they just as much created me.her comrades. >> reporter: we caught up with cornwell in knoxville, tennessee. where she is a major benefactor. and she and i don protective gear to look at how human blood spatter evidence really works. nicely done. and this is the key to her phenomenon success. when it comes to crime scenes, blood, bullets, knives -- >> this is more for decapitating people. >> reporter: patricia cornwell really knows her stuff. >> that's interesting. a very different pattern than the baseball bat. >> reporter: talk about the blood evidence like it's eloquent. >> blood likes to tell what happened. it's the life force, just determined not to let you get away with it. >> reporter: that passion, that conviction, as the murdered dead speak to us through crime scene evidence. that's what's always driven her and her alter ego, kay scarpetta. what is it about what kay scarpetta does that thrills so many readers? >> it's tapping into a part of human nature that is so fundamental and so strong in all of us, wh