Forensic science evolved through frustration, innovation, and sensation.
Posted Feb 04, 2014
District Attorney Sohn, also the chief investigator, had read an article celebrating German chemist Georg Popp as a modern-day Sherlock Holmes. He invited Popp into the case.
Popp had become fascinated with the application of chemistry to forensic analysis after successfully analyzing spots on a suspect’s trousers. He’d also identified a thief in his own lab by using vapors to expose a latent fingerprint.
In the case of the headless corpse, a local bully named Andreas Schlicher was the chief suspect, and scorings from under his fingernails had yielded traces of human blood. Popp requested the man’s clothing for microscopic analysis, but Sohn refused to send them.
As I discovered when I wrote Beating the Devil’s Game, despite curiosity about scientific methods, there was also plenty of resistance. Forensic science did not find a ready welcome from traditional investigators or judges. It had to prove itself, step by step.
Eventually, another detective took over the Filbert case and he sent Popp the requested clothing. Popp found evidence of blood on the shirt and trousers, with obvious attempts to wash it off. He also examined the suspect’s shoes. They bore several layers of soil with embedded purple and brown fibers. Part of the sample was similar to soil from the crime scene. None wassimilar to soil from other places the suspect claimed to have been.
Popp used a spectrophotometer to compare the spectrum of emission lines from dyes in the fibers. He found that the purple and brown fibers stuck on the shoes were identical in color and consistency to the victim’s skirt.
In the first documented case to focus on soil analysis and the chemical composition of fiber, a jury found Schlicher guilty, based largely on this impressive physical evidence. He then admitted his deed. He’d hoped to rob the woman, he said, but when she had no money, he’d killed her out of anger and removed her head. The posing was just to humiliate her.
My favorite cases from this era involve someone innovating a way to meet a challenge.
For example, British chemist James Marsh met his match with a jury, but he didn't admit defeat. The case involved the death of George Bodle in 1832 after drinking coffee. His symptoms, along with a strained relationship with his family, suggested poisoning.So did the circumstances.
On the morning of his death, Bodle’s grandson, John, had filled a kettle from the well, a behavior that the maid said was uncharacteristic. This kettle had been used to brew the coffee.
However, it wasn't just a matter of finding arsenic in the victim. At the time, arsenic could be detected in human organs, but there was as yet no method for measuring quantity, and defense attorneys were suggesting other ways that arsenic could enter the body, such as from hair products.
But Marsh had figured it out. With his own unique method, he tested the kettle and coffee from that fatal morning, and found traces of arsenic. Confident, he testified about his findings before a jury. Unfortunately, they had no idea what he was saying and his demonstration failed to clarify anything. The jury declined to convict.
Frustrated, Marsh went back to the drawing board. Should he ever have another case, he decided, he needed a better way to show how the method worked.
Marsh was conversant with a heating process that transformed arsenic into a visible black deposit, but since the arsine gas escaped into the air, it was possible to miss small traces that were present. Marsh had to figure out how to contain it all and also how to show it as proof. In a sealed bottle, he treated poisoned material with sulphuric acid and zinc. From this bottle emerged a narrow glass tube that captured the escaping gas. Here, it could be ignited with heat to form the black deposit. Thus, he could measure the total amount of arsenic and show it to a jury.
Then he got the chance to show a jury. Marsh successfully used this method, which became known as the Marsh Test, in another case.
Oh, and he’d been right about the poisoning of George Bodle. A decade later, John Bodle confessed.