Crime Library: Criminal Minds and Methods

Forensic Toxicology

Heavy Metal

Robert Curley, 32, began to grow ill in August 1991, entering the hospital in Wilkes-Barre, Pennsylvania, for what would become a series of stays before he finally died in September.   His doctors went through several diagnoses for his puzzling symptoms, which included burning skin, numbness, weakness, repeated vomiting and rapid hair loss.  Just before he died, he became more agitated and aggressive, so he was transferred to a hospital that could perform tests for heavy metal exposure.  Sure enough, he had elevated levels of thallium in his system. 

First discovered and named in England in 1861, this carcinogenic substance had been applied in limited doses for ringworm, sexually transmitted diseases and gout.  It was also used in rat poison but was eventually banned in 1984.  

Mortal Evidence
Mortal Evidence

A search of his worksite at Wilkes University turned up five bottles of thallium salts in a stockroom for the chemistry lab, but none of his co-workers had experienced any symptoms from inadvertent thallium exposure.  The levels measured in Curley at autopsy were so high it was determined that he'd been deliberately poisoned, and his death was ruled a homicide via severe hypoxic encephalopathy, secondary to thallium poisoning.  In other words, as Cyril Wecht describes it in Mortal Evidence, his brain had swelled so much it had pushed down into the spinal cord.

Investigators searched the Curley home, where Joann, his wife of 13 months, lived with her daughter from a previous marriage.   They found several thermoses that tested positive for thallium, which Mrs. Curley said her husband used to take iced tea to work.  In addition, tests done on Joann and her daughter showed elevated levels of thallium, but not in such toxic proportions.

With no leads on suspects, however, the case went cold.   Curley's widow, Joann, sued the university for wrongful death.  She had recently collected over one million dollars from a car accident involving her first husband, and she had gained $297,000 in life insurance from Robert's demise.  She looked suspicious to the police, but they had no way to prove that she had killed her husband.

Dr. Frederic Rieders
Dr. Frederic Rieders

Authorities approached Dr. Frederic Rieders of National Medical Services, a private toxicology lab in Willow Grove with extensive testing abilities, to do a more thorough analysis of the tissues.  Rieders requested more samples, so Joann agreed to have her husband exhumed.  Hair shafts were removed from various parts of Curley's body, along with toenails, fingernails, and skin samples.

Dr. Reiders conducted a segmental analysis on the hair shafts to devise a timeline of thallium exposure and ingestion.   The hair strands from Curley's head were sufficiently long to plot approximately 329 days of his life prior to his death.  Thallium levels were recorded in the hair shafts at different times using atomic absorption spectrophotometry.  That means Rieders used a chemical to break down each segment of hair into individual atoms and then excited them to the point where they absorbed energy.  Every substance has an individual, measurable absorption rate, and through this method, the quantity of the substance can be determined.

The results were surprising.   While investigators had figured August 1991 as the initial exposure period, concentrations of thallium were measured over the course of nine months, with spikes and drops that suggested a systematic ingestion long before Curley had begun his job at the university.  Clearly, that was not where he had first received his exposure to thallium.  There was also a massive spike just a few days before his death that suggested intentional poisoning.  Hair from other parts of his body, as well as readings from his toe- and fingernails, supported this data.

This timeline was compared to events in Curley's life, which indicated that when he was away from home or in the hospital, his thallium levels dropped—except for the few days prior to his death.   At that time, his family had brought in some food and his wife was alone with him.

The pressure was now on Joann Curley, and in 1997 in a plea deal she confessed to having murdered her husband with rat poison in order to enrich herself on his life insurance payment.   In the deal, she received a sentence of 10-20 years in prison.

While metal-based poisons received the most attention during the early years of forensic toxicology, once they became detectable, they tended to lose their appeal as a means for murder.  The plant-based toxins drew the attention of killers.


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