On a weekend in October, when much of the country glows under a cloudless sky, Ann Rule is reached in the dim corridors of a hotel in Pensacola, Fla., at a convention of medical examiners. It is a highly specialized group -- doctors, dentists, criminalists -- people whose job it is to study a murder scene, analyze the sprawl of a corpse, measure surrounding drops of blood, calculate time of death, profile the mind of the killer.

One of the conventioneers, a dentist, has brought her "cadaver dog," a terrier trained to sniff out human body parts in any state of decomposition. Someone in the audience takes a chip of gold crown with nothing on it save a speck of human tooth enamel and hides it in a Tootsie Roll wrapper on a table high off the floor with two folding chairs on top. When the dentist admits the dog, it sniffs the air, trots smartly past the living, and makes a quick beeline for the tiny hint of death. There is wild applause, much congratulation, laughter all around.

After one of the sessions, Rule is approached by a criminalist: "Do you want to see my new software?" the woman asks excitedly. It has pictures of Ted Bundy. But the images offered to Rule will be unlike any she's ever seen of the serial murderer. They are post-electrocution.

It takes a particular kind of writer to be in this line of work: curious, methodical, morbid, able to dissociate, fascinated by twisted minds, driven to avenge the victims. A longtime writer of true crime, Ann Rule is all of these. She has produced 18 books with titles like A Rage to Kill, Bitter Harvest, In the Name of Love, A Fever in the Heart, You Belong to Me, The Stranger Beside Me, Small Sacrifices, and her latest -- And Never Let Her Go (about the Thomas Capano murder case).

She was born in Lowell, Mich., in the late '30s. Her father was a high-school track coach. Her mother worked with the disabled. Rule spent her girlhood summers in Montcalm County, where her grandfather was the sheriff, and where jail, office and family quarters were all under one roof. Her grandmother cooked for the prisoners; Rule's job was to carry dinner to each prisoner, shoving the plate through the trap on the cell door. "I would find myself wondering why anybody would disobey the law," she says. "By 8, I knew I wanted to be a policewoman."

As Rule grew up, her father coached track at several colleges, including the University of Michigan. When she graduated from high school, she attended Willamette, then Oregon State, then the University of Washington. After completing her M.A. in criminal psychology, she was hired by the Seattle police.

But policewomen were different from the way they are now. "We were glorified caseworkers. We didn't wear uniforms. A badge and a bus pass were all we were given. If things got dangerous, we were told to call for a male back-up."

She married an English teacher, quit work so that they could have a family. But when she and her husband divorced and he subsequently died of cancer, she was left with four young children to support. That's where the writing came in. At first, she did public surveys, going door to door, writing up opinions for a modest fee. Then she began placing articles in True Confessions, a pulp magazine that didn't require her to sign her name. Eventually she was hired by True Detective, covering two cases a week for $200, under the name Andy Stack. She went back to school, studied police science, learned what to look for in a crime scene -- how to collect fingerprints, how to record evidence, how to judge the distance from wound to blood splatter by the relative shape of one drop. Before long, she was writing about such things "for the slicks": Cosmopolitan, Redbook, Ladies Home Journal.

Come the '70s, she was an active counselor at the Seattle Crisis Clinic, a group organized to counsel the families of victims of violent crime. Her partner was Ted Bundy, a psychiatry student at the University of Washington. Two nights a week, she holed up with Bundy in the house that served as the Clinic's headquarters, listening to bereaved callers whose family members had been found murdered. In the wee hours of morning, Bundy would walk her to her car, caution her that the world was a sick place. When it was revealed that Bundy himself had murdered a string of women up and down the western United States, Rule decided to write her first book, The Stranger Beside Me.

Since then, Ann Rule has written a great deal about the Bundys of this world: highly intelligent people (Bundy's IQ was 124, Diane Downs's was 139) with complex psychological disorders and a predisposition for murder. It's a genre of writing that is relatively new; there are no old masters to show the way. Great writers have tried their hand at it: Gabriel Garcia Marquez, Truman Capote, Diana Trilling; but few do it more than once. To take up the task again and again, as Rule does, and to dedicate a career to plumbing the killer mind, is rare indeed.

"It's difficult work," she says. "My writing at first is always angry. Mornings I go back and erase my personal feelings. I couldn't do it if I didn't have some religious faith; and if I didn't think the victims were helped by what I do."