The Big Idea: Adam Schrager

I’ve known Adam Schrager since we were both college newspaper editors (me at University of Chicago, he at Michigan). While I eventually abandoned journalism for a career of making things up for a living, Adam’s kept at it, finding fascination in real life stories as an investigative reporter. In his latest book, The Sixteenth Rail, Adam uses those journalism skills to tell the story of one of the great crime dramas of the 20th century, and how it was solved — by science.


I remain convinced I could have solved one of the great criminal mysteries of all time if my older sisters had not complained to my parents that I was being annoying.

It was 1977 and we were traveling along the west coast, where five-plus years earlier a man named D.B. Cooper, wearing a dark suit, had parachuted out of a 727 airplane with a $200,000 ransom. I had brought a well-worn, green, hard cover book chronicling the country’s top crimes on our family trip and to this aspiring 7-year-old detective, every man I saw in a dark suit was a lead worth calling 9-1-1 to report.

The fact that in the nearly six years since the hijacking, he had likely changed outfits was lost on me. However what I retained from that vacation, besides the fact that my sisters were not as enterprising as me, was a vivid memory of the chapter chronicling the kidnapping of Charles A. Lindbergh, Jr. (a.k.a. “The World’s Baby”).

The son of the first man to fly solo across the Atlantic Ocean was snatched from his nursery late on the night of March 1, 1932. The police report chronicled the complete list of evidence as: a ransom note, a standard carpenter’s chisel and a homemade, three-piece, sectional ladder.

Lindbergh Sr. was quite simply the most popular man in the world at the time, his extraordinary feat led to his receiving 3.5 million letters within weeks of his landing in Paris. His friend Fitzhugh Green wrote, “There was a definite phenomenon of Lindbergh quite the like of which the world had never seen.”

After lead after lead evaporated and the maze of theories led to dead end after dead end, the pressure to solve the crime grew exponentially when the 20-month-old boy was found dead. “There can be no immunity now,” moviegoers heard on the newsreel in the summer of 1932. “It is up to America to find the perpetrator of this crime or it is to be America’s shame forever.”

In his own kitchen in Madison, Wisconsin, a soft-spoken, balding, government scientist looked across the table at his own young son, just 48 days older than Charles Jr., and “I shuddered.” Unlike the rest of America though, Arthur Koehler’s next reaction was less predictable.

“I grew excited,” he would later tell The Saturday Evening Post. “You see, that ladder, because it was made of wood, seemed just like a daring challenge.”

Arthur Koehler had literally written the book on wood, “The Properties and Uses of Wood,” released in 1924. He was employed by the Forest Products Laboratory, the world’s pre-eminent research laboratory into trees and wood, and in that context, he felt he could help investigators as it pertained to what would become the single most recognizable piece of criminal evidence until the bloody glove in the O.J. Simpson trial seven decades later.

As a reporter, I’m always fascinated by people who describe themselves as ordinary and yet, when they’re placed in extraordinary situations, they act extraordinarily. Side note, my crime fighting stalled out as did my desire to play left field for the Chicago Cubs so as we are wont to say in journalism, “Those who can’t, write about those who can.”

Nearly a year after the crime was committed, Koehler was asked by the FBI and the New Jersey State Police to see if he could make the wooden witness talk. Unlike the convenience of the 60-minute episodes of CSI and other television programs of its ilk, the investigation was tedious, the research meticulous and the time consumed lengthy.

Over the course of the next year and a half, he would discover microscopic anomalies on two of the ladder’s rails, track them to the lumber yard in South Carolina where they were machine-planed, and then to the New York mill where the lumber was sold, only to hit a dead-end when it was revealed the store did not keep sales records.

But his more important discovery was his analysis of Rail No. 16, the upper-left hand section of the ladder. Unlike every other part of the ladder, it was hand-planed on both ends, instead of being machine-planed. The piece also had previous nail holes, none of which had any rust around them, leading Koehler to tell investigators that the piece likely came from the inside of a building, maybe even an attic.

When Bruno Richard Hauptmann was arrested in September, 1934 after spending one of the bills used to pay the ransom and a gas station clerk wrote down his license plate number. Detectives found more of the ransom money in Hauptmann’s home and garage and, as it relates to the ladder, a ripped up board in his attic.

Using technology known to few at the time, Koehler analyzed the tree rings from the board in the attic, compared it to the 16th rail and concluded they matched. This was four years before the first tree-ring laboratory would be created at the University of Arizona and the principle that one ring would represent a year in the life of that tree was not commonly known.

In fact, when prosecutors sought to call Koehler as a witness in Hauptmann’s trial, the defense counsel protested, saying “There’s no such animal known among men as an expert on wood.” Even the government lawyers didn’t understand Koehler’s science, but knew his testimony would “wrap the kidnap ladder right around Hauptmann’s neck.”

His testimony wowed the worldwide media collected to cover what H.L. Mencken called, “the greatest story since the Resurrection.” Koehler was described as “Sherlock Holmes in the witness box,” and The New York Post, realizing the importance of his testimony, presciently wrote: “The Hauptmann trial may go down in legal history less as the most sensational case of its time than as the case which brought legal recognition to the wood expert on a par with handwriting, fingerprint and ballistic experts.”

And that’s the big idea of Arthur Koehler, who can honestly be called the father of forensic botany. He was the final prosecution witness in the trial of the century, one which led the FBI and law enforcement agencies worldwide to embrace scientific methods as aids in solving crimes. It’s standard fare now to see DNA tests, lab results, scientific analysis in not just the sensational trials, but the every-day criminal case as well.

“While a scientist must be truthful in his observations,” Koehler told NBC Radio after the guilty verdict was announced, “he must also have the capacity to let his imagination wander along restricted channels so as to realize the possibilities to which those observations may lead. This is particularly true in scientific detective work, because the observations are of little value unless clues can be properly interpreted and followed up.”

Specifically, in Arthur Koehler’s case, he was consumed with the fidelity and reliability of trees. “A tree never lies,” he was fond of saving. Not surprisingly, in retirement, he would consult with the creators of the Perry Mason program, one of the first truly successful crime-solving programs on television.

The science of Koehler’s tree-ring testimony withstands all of the conspiracy theories surrounding the Hauptmann trial, but it also leads to a secondary big idea. There remain trees to be analyzed, original data to be explored and studied, and a continuing need for the so-called “classically-trained scientist.”

“Koehler’s legacy,” said Dr. Shirley Graham, who is a curator at the Missouri Botanical Gardens, “was to show how basic descriptive science still has modern value and important applications.”

I hope you agree. Now, I just need to convince my sisters to unplug their ears thirty-plus years later to listen to my latest theory as to where D.B. Cooper might be.


The Sixteenth Rail: Amazon|Barnes & Noble|Indiebound|Powell’s

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