In the wake of a disaster, the complexities of identifying one fragmented body by comparing its teeth with the dental records of scores of probable victims can often take hours--and that's just to make a good guess that may be confirmed by later comparing X-rays.
Army Col. Lewis Lorton, 46, has found a way to cut that preliminary process of elimination down to an average of about four minutes.
Which is why Lorton, a member of the Army Institute of Dental Research in Washington, has spent the last several days in Los Angeles, peering at a small computer screen in the bowels of the county coroner's office, formulating advice for coroner's staff members as they work to identify the 85 people who are believed to have been killed in the Cerritos air disaster.
Impatient with the time and mental concentration needed to make preliminary matches, Lorton has developed a new computer program that runs through thousands of dental identification variables that have traditionally been sorted by hand.
He designed the program for the military and first put it to use last December during the effort to identify the 256 American soldiers and crew members killed in a chartered jetliner crash in Gander, Canada.
"It's a very effective way to sort people out," said Lorton, who was drafted out of private dental practice in 1966 during the Vietnam War military buildup and has stayed in the Army ever since.
Officials in the Los Angeles coroner's office, familiar with his work, invited him here for assistance and the Army obliged.
Lorton, still red-eyed from jet lag after flying to Los Angeles Wednesday from his base at Walter Reed Army Medical Center, said he hopes he can help speed up the identification process. However, he emphasized that he is not sure how effective he will be because his program was designed to identify military personnel, not civilians.
"In the military, you normally have far better antemortem (pre-death) records to work from," he said. The military population is also more predictable in terms of age, sex and race.
Normally, medical identification specialists begin with two stacks of dental charts: one stack of antemortem sheets, diagramming all known dental work for each person believed to be a victim, and another stack of post-mortem sheets, diagramming the dental characteristics of each unidentified body. Each post-mortem chart is compared against all of the antemortem charts until probable matches evolve.
Some variables make this identification easy. It is rare, for example, for one person to have two crowns.
But the sheer number of variables, multiplied by the number of victims, makes the task intimidating and prey to human factors like fatigue, Lorton said.
"Each mouth normally has 32 teeth, and each tooth can be in one of 26 different types of conditions," he said.
For example, because a filling can be applied to any one of five surfaces on a tooth, "If you're between 18 and 25 years old and have five or six dental filings, there's a chance that there will be no one like you among 700 people," Lorton said with the panache of a confessed statistics buff.
The beauty of feeding these globs of data into a machine is that it can quickly match the antemortem and post-mortem charts of such a person without being intimidated by the surrounding mass of other variables.
Lorton's computer program spits out a sheet for each unidentified body, listing the relative probability that it can be matched to any of the antemortem charts.
As an example, he held up one sheet that found 10 "matching" teeth between one antemortem chart and one post-mortem chart. Because the computer had found no contradictory "mismatches," the positive identification seemed probable.
First, however, dental X-rays would have to be compared, a process in which Lorton is not routinely involved.
"I don't even look at the specimens," he said. "I look at the paper work."